Claude or GPT for building things?
For a small, clear build both got it right first time and one cost about a fifth of the other, so the cheaper, faster agent is often enough.
What the reel showed
One brief to two AI coding agents: a Breakout game in a single web page that plays itself, with a score and lives and no click needed. Claude Fable 5.1 ran in Claude Code, GPT-6 Astra in Codex CLI. One attempt each, in a fresh empty folder.
Both shipped a game that runs and plays itself. Fable built a tall portrait board in 4m19 for $2.27. Astra built a wide board in 2m23 for $0.47.
Fable took two turns and wrote about 23,000 output tokens, much of it thinking. Astra answered in one pass with about 4,200.
| Entrant | Tool | Time | Cost | Verdict |
|---|---|---|---|---|
| Claude Fable 5.1 | Claude Code | 4m19 | $2.27 | Plays itself, portrait board |
| GPT-6 Astra | Codex CLI | 2m23 | $0.47 | Plays itself, wide board |
Each model ran in its maker's coding agent, Claude Code and Codex CLI, one attempt each; costs are read off each run's own bill and can differ from the figures shown in the reel.
What this means for your business
Nobody needs a Breakout game. Plenty of businesses need small tools built: a quote calculator for the website, an intake form, a price list page, a one-page tool that turns a spreadsheet into something a customer can read.
When the task is clear and easy to check, both of these agents get it right the first time, and you do not need the most expensive setup. The bill here was about 4.8 times apart for the same result.
Where you run a model matters about as much as which model you pick. Claude Code wraps every call in a lot of instructions before your brief arrives, and that lands on the bill, or on your plan's usage limits. Save the heavier setup for work with many steps, work that has to check itself, or work inside a large codebase.
What I’d use
For small one-file tools I try the cheaper, faster agent first and only move up if it misses. For long builds inside a real project I still reach for Claude Code, because it checks its own work, and that is worth the extra cost there.
Both are good. Run one small build of your own through both, then pick.
Try it yourself
Build one small tool your business would actually use, in both agents, and compare the result, the time and the cost. Both agents run on subscriptions you may already have.
Route A: Claude Code on your Claude plan
Anthropic's coding agent, included with Claude Pro and Max. This is how I work every day: runs draw on your plan's usage limits instead of a bill per call, so you can experiment freely. Fable is included on Max; on Pro it runs on paid usage credits.
Route A: Codex CLI on your ChatGPT plan
OpenAI's coding agent. Run it and choose Sign in with ChatGPT to use it on a ChatGPT Plus, Pro, Business, Edu or Enterprise plan, which is how I run Astra day to day.
Start each one in its own empty folder
Make two new empty folders, start one agent in each, and paste the same brief. Do not help either of them. You are testing what each does on its own.
Build a quote calculator for my business as a single HTML file called quote.html. My business: [one line, e.g. "We clean offices in Bangkok."] Pricing: [your real rules, e.g. "1,500 baht per visit plus 8 baht per square metre, 10% off weekly contracts."] The page should: - ask for the inputs a customer knows (size, how often, extras) - show the price live as they type, with a short breakdown - have a "Send me this quote" button that opens an email to [your email] with the details filled in - look clean on a phone No external libraries. When you are done, open it and check the maths with two examples.
Test both like a customer
Open both quote.html files in your browser. Price three real jobs and check each total by hand. Note how long each agent took.
Route B: no subscription or no terminal? Use OpenRouter
One OpenRouter account and key covers both models, pay per use. Paste the same brief into OpenRouter's chat with Claude Fable 5.1 and GPT-6 Astra selected. Copy each answer into a text file, save it as quote.html and double-click it.
Something I haven't tried yet, but you can
Higgsfield, an AI image and video platform, has an official MCP connector for AI agents. In Claude Code you can ask the agent to set up Higgsfield for you, and Codex CLI can add it as an MCP server. Then the same agent that built your tool could make a short promo video or ad images of it for your socials. It uses a paid Higgsfield plan and its credits. I have not tested this, so treat it as an idea to try.
Links
- Claude CodeAnthropic's coding agentclaude.com
- Claude Code with Pro or MaxRun it on your Claude subscriptionsupport.claude.com
- Codex CLIOpenAI's coding agent, signs in with a ChatGPT plangithub.com
- GPT-6 AstraOpenAI's announcementopenai.com
- OpenRouter chatSend one prompt to several models side by sideopenrouter.ai
- Claude Fable 5.1 on OpenRouteropenrouter.ai
- GPT-6 Astra on OpenRouteropenrouter.ai
- Higgsfield MCPHiggsfield's official connector for AI agentshiggsfield.ai
Need a small tool built for your business?
Quote calculators, intake forms, internal dashboards. Trying it yourself is a good start. Getting it live and connected to your email and your data is what I do.