Is DeepSeek as good as ChatGPT?

Not across the board in our September 2026 round. GPT-6 Astra won 9 of 10 prompts in a blind review with zero hallucinations. DeepSeek V4 Pro matched it on every calculation and won the bill split puzzle, but produced two partials, one factual slip and one unfinished task.

Is DeepSeek cheaper than ChatGPT?

Yes. Measured in Krater, the ten DeepSeek V4 Pro answers cost $0.11 in total against $0.23 for GPT-6 Astra, and on short prompts DeepSeek was often ten times cheaper. On the coding prompts the gap closed because DeepSeek spent heavily on reasoning tokens.

Why did DeepSeek fail the JavaScript task?

DeepSeek V4 Pro reasoned for about 14,700 tokens on the off by one cent bug and did not return an answer within the Arena's time limit in two attempts. A direct API call finished after 197 seconds. We score what the model delivered under the same conditions as the others, so it counts as a fail.

Can I use DeepSeek and ChatGPT in the same place?

Yes. Krater gives you DeepSeek V4 Pro, GPT-6 Astra and 400+ other models in one workspace, and the Model Arena lets you send one prompt to several models side by side, which is how this comparison was run.

How was this comparison tested?

All three models (GPT-6 Astra, Claude Fable 5.1 and DeepSeek V4 Pro) received the same ten prompts side by side in the Krater Model Arena on 16 September 2026, with default settings and no system prompt. We recorded time to a complete answer and the model cost per answer, fact checked every claim against a primary source, scored task completion as pass, partial or fail, and then Malte and Vitus Pruser ranked the answers blind, without knowing which model wrote which. The full procedure is on our methodology page.

Will this comparison be updated?

Yes. Flagship comparisons are rerun monthly and whenever a provider ships a new version. The tested month and model versions are shown at the top of the page.

DeepSeek vs ChatGPT: 10 tasks tested side by side (September 2026)

Tested: September 2026 with DeepSeek V4 Pro and GPT-6 Astra, by Vitus Pruser.

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