Which AI Should I Choose?
Subscription vs API key + costs + region | Illustrated guide + decision flowchart | About a 5-minute read
Scholardo itself doesn't charge you for AI usage, but the AI services it drives (Claude Code / DeepSeek / Codex) require you to open an account with the corresponding vendor and pay them directly. The picker inside the app won't tell you "this costs money," so please read this page before you choose — pick the right path and every later step goes smoothly; pick the wrong one and you may get stuck at sign-up or payment with no way forward.
One-Line Answer (TL;DR)
- You're in mainland China → choose DeepSeek (sign up with a Chinese phone number, top up with common domestic payment methods) → see P0-3 "DeepSeek Full Setup (First Choice for Mainland China)". Users in mainland China typically cannot register a Claude subscription or a ChatGPT subscription — go with DeepSeek.
- You can sign up for overseas services and want a "fixed monthly fee, no bookkeeping" experience → choose Claude Code (get a Claude subscription) → see P0-1 "5 Minutes: From Download to Your First AI Conversation (Claude Subscription Edition)".
- You already pay for a ChatGPT subscription → choose Codex and reuse the ChatGPT subscription you already have — no need to pay twice.
Decision Flowchart
【Figure 1: custom decision flowchart — see the Shot list at the end】
flowchart TD
A[Start: which AI should I choose?] --> B{Are you in mainland China?}
B -- Yes --> C[Choose DeepSeek<br/>Sign up with a Chinese phone number, top up domestically<br/>→ Read P0-3]
B -- No / I have an overseas phone number and card --> D{Do you already subscribe to ChatGPT?}
D -- Yes --> E[Choose Codex<br/>Reuse your existing ChatGPT subscription — no double payment]
D -- No --> F{How do you prefer to pay?}
F -- Fixed monthly fee, same price no matter how much I use --> G[Choose Claude Code<br/>Get a Claude subscription<br/>→ Read P0-1]
F -- Pay as I go, start with a small amount --> C2[Choose DeepSeek<br/>Top up a balance + API key<br/>→ Read P0-3]If your browser doesn't render the chart above, here's the text version:
- Are you in mainland China?
- Yes → choose DeepSeek. Users in mainland China typically cannot register a Claude subscription or a ChatGPT subscription — go with DeepSeek. Mainland Chinese phone numbers and bank cards generally can't complete sign-up or payment for those two, so don't waste time on those paths. → Read P0-3.
- No → go to question 2.
- Do you already subscribe to ChatGPT?
- Yes → choose Codex and reuse your existing subscription.
- No → go to question 3.
- How do you prefer to pay?
- Fixed monthly fee, no bookkeeping → choose Claude Code (Claude subscription). → Read P0-1.
- Pay only for what you use, start small → choose DeepSeek (top-up + API key). → Read P0-3.
The Three Engines Compared
| Claude Code | DeepSeek | Codex | |
|---|---|---|---|
| Who's behind it | Anthropic (the Claude models) | DeepSeek | OpenAI (same family as ChatGPT) |
| What account you need | A Claude subscription account (Claude Pro / Max tiers — you sign in with the vendor account, not an API key) | A DeepSeek open-platform account + one API key | A paid ChatGPT subscription account (you sign in with the vendor account, not an API key) |
| Where to sign up | claude.ai / anthropic.com | platform.deepseek.com | chatgpt.com / openai.com |
| How you pay | Monthly subscription: a fixed fee per month; tiers and prices as shown on the vendor's current page at anthropic.com (Claude subscription pricing) | Pay as you go: top up a balance on the platform, create an API key, and usage is deducted from the balance; unit prices as shown on the vendor's current page at platform.deepseek.com | Monthly subscription: comes with your ChatGPT subscription; tiers and prices as shown on the vendor's current page at openai.com / chatgpt.com (ChatGPT pricing) |
| Best for | People who want a "fixed monthly fee, just use it" experience and don't want to watch a balance | Users in mainland China; light users who want to pay as they go and try it out with a small amount first | People who already pay for a ChatGPT subscription and don't want to open another one |
| Availability in mainland China | Usually unavailable: mainland phone numbers / bank cards generally can't complete sign-up and payment | Available: sign up with a Chinese phone number, top up with common domestic payment methods | Usually unavailable: mainland phone numbers / bank cards generally can't complete sign-up and payment |
【Figures 2, 3, 4: screenshots of the three vendors' pricing pages — see the Shot list at the end】
You may also see more models in Scholardo, such as Kimi and GLM: they're not "paste a key and go." They run piggybacked on Claude Code (on first launch, Claude Code is installed automatically as the carrier). That's an advanced setup and out of scope for this page — if you need it, see the advanced guide "Kimi / GLM / Custom Integrations" (P2-3).
Subscription vs Pay-as-You-Go — What's the Actual Difference?
A monthly subscription is like a gym membership: you pay a fixed fee every month, and normal usage during that period isn't billed separately (each tier has its own usage limits — see the vendor's site for details). Claude Code and Codex both work this way — you sign up on the vendor's website (claude.ai or chatgpt.com), add a card, subscribe, and then sign in with that account inside Scholardo. You'll never touch anything called an "API key" — it's just a normal account sign-in. This suits people who don't want to do bookkeeping and use AI every day: during a paper-writing crunch you can use it freely, with no surprise bill at the end of the month.
Pay-as-you-go (API key) is like a prepaid transit card: you load money onto the account first, and each use deducts from the balance based on actual usage — use less, pay less; use nothing, pay nothing. DeepSeek works this way — you sign up at platform.deepseek.com, top up, and then create an API key (a string starting with sk-, effectively the "withdrawal PIN" for your account) and paste it into Scholardo's settings. This suits two kinds of people: light users who just want to spend a small amount to try things out, and people who simply can't register a subscription at all — which is the situation for most users in mainland China; see the next section.
One line to remember the difference: subscription = sign in with the vendor account, fixed monthly fee; pay-as-you-go = top-up + API key, pay only for what you use.
If You're in Mainland China
Important: users in mainland China typically cannot register a Claude subscription or a ChatGPT subscription — go with DeepSeek. Mainland Chinese phone numbers and bank cards generally cannot complete sign-up and payment for those two services. This is not a Scholardo limitation — it's a consequence of those vendors' service coverage. Please don't keep retrying sign-up or card binding on those two paths — it will most likely fail, and may cost you time and money.
The reliable path for mainland users is DeepSeek:
- Sign up at platform.deepseek.com with a Chinese phone number;
- Top-ups support common domestic payment methods;
- After topping up, create an API key, paste it into Scholardo, and you're set;
- Prices as shown on the vendor's current page at platform.deepseek.com.
For the complete step-by-step illustrated walkthrough (every screen from sign-up, top-up, and key creation to getting it running inside Scholardo), see P0-3 "DeepSeek Full Setup (First Choice for Mainland China)".
If you're physically in mainland China but have a fully working overseas phone number and payment card, the subscription route is theoretically possible — but this guide doesn't recommend it for non-technical users. DeepSeek is the hassle-free choice.
Made Your Choice? Next Step
| Your choice | Next tutorial |
|---|---|
| Claude Code (Claude subscription) | P0-1 "5 Minutes: From Download to Your First AI Conversation (Claude Subscription Edition)" |
| DeepSeek (top-up + API key) | P0-3 "DeepSeek Full Setup (First Choice for Mainland China)" |
| Codex (ChatGPT subscription) | "Enabling Codex in Settings + Sign-in Screen by Screen" (P1-1, coming soon) |
Shot List (Figures to Prepare)
| Shot # | What to capture / draw | Source | Callout notes |
|---|---|---|---|
| Fig 1 | Finished decision flowchart (redraw the mermaid chart above in brand style) | Custom illustration | Highlight the first fork — "Are you in mainland China? → Yes → DeepSeek" — in a prominent color |
| Fig 2 | Anthropic's Claude subscription pricing page (vendor UI / captured as-is / do not fabricate or redraw / do not annotate specific price figures) | Vendor UI (anthropic.com / claude.ai pricing page) | Box "this is the monthly subscription tier page"; caption reads "prices as shown on the vendor's current page" |
| Fig 3 | OpenAI's ChatGPT subscription pricing page (vendor UI / captured as-is / do not fabricate or redraw / do not annotate specific price figures) | Vendor UI (openai.com / chatgpt.com pricing page) | Box "Codex reuses this same ChatGPT subscription"; caption reads "prices as shown on the vendor's current page" |
| Fig 4 | DeepSeek open-platform pricing / top-up page (vendor UI / captured as-is / do not fabricate or redraw / do not annotate specific price figures) | Vendor UI (platform.deepseek.com pricing page) | Box the "top up a balance + pay-as-you-go billing" entry point; caption reads "prices as shown on the vendor's current page" |
| Fig 5 | Scholardo's agent chooser when creating a new session. Note: only the Claude Code row shows by default — Codex/DeepSeek appear only after you enable/add them in Settings (see P0-1 / P0-3) | Scholardo UI | Annotate "this screen shows no costs — cost awareness comes from this page" |
| Fig 6 | "Subscription vs pay-as-you-go" comparison illustration (left: gym membership = sign in with the vendor account; right: prepaid transit card = API key + balance) | Custom illustration | One small caption line on each side: "fixed monthly fee / pay only for what you use"; on the API key side, sketch "a string starting with sk-" |
Common Pitfalls / FAQ
Q1: I'm in mainland China — can I use a Claude or ChatGPT subscription? Usually not. Sign-up requires an overseas phone number and payment requires an overseas bank card; mainland numbers and cards generally don't get through. Don't keep retrying — go straight to DeepSeek (see "If You're in Mainland China" above and P0-3).
Q2: With pay-as-you-go, could I suddenly get charged a lot? DeepSeek uses a top-up-first, deduct-later model: what you spend comes out of the balance you loaded in advance, and balance rules and unit prices are as shown on the vendor's current page at platform.deepseek.com. The safe approach is to top up a small amount the first time, use it for a few days, check your actual consumption on the platform's usage page, and then decide whether to add more.
Q3: I've entered my API key — why does choosing Kimi (or GLM) still install something? Because third-party models like Kimi / GLM run piggybacked on Claude Code — Claude Code acts as the carrier here, and Scholardo installs it automatically for you on first launch. What's installed is the carrier; you are not being asked to pay for a Claude subscription. See the advanced guide (P2-3).
Q4: Does a subscription mean "unlimited usage"? No. Every subscription tier has its own usage caps or rate limits — see the vendor's current site for specifics. For most day-to-day paper-writing workloads, a regular tier is usually enough; if you keep hitting the ceiling, consider upgrading.
Data Privacy Disclosure
Whichever engine you choose, please be aware: your manuscript content is sent to your chosen AI provider (Anthropic, DeepSeek, or OpenAI) for processing. When you ask the AI in Scholardo to read, summarize, or polish your paper, notes, or references, the relevant text is transmitted over the network to the servers of the provider you selected, where it is handled under that provider's privacy policy. Scholardo only sends the necessary content when you actively start an AI conversation; it never uploads your local files without your knowledge. But how the data is handled once it leaves your machine is governed by each provider's own privacy policy — we recommend skimming the privacy terms on the vendor's website before signing up. If your research materials involve unpublished data, participant privacy, or confidentiality agreements, first confirm that sending them to a third-party AI service complies with your institution's requirements.