GPT-5.5 vs DeepSeek-V4-Pro
GPT-5.5 wins on Overall, Multimodal; DeepSeek-V4-Pro wins on Coding. Every numeric field is compared below, with a worked monthly-cost example and a pick rule for each use case.
Verdict at a glance
Choose GPT-5.5 if you…
- Balanced with no weak spot
- Richest ecosystem
- Mature plugin/function calling
- Strong creative writing
- Best for: General tasks, Creative writing, Coding
Choose DeepSeek-V4-Pro if you…
- Strongest open source
- Value champion
- Excellent math reasoning
- Extremely low price
- Best for: Coding, Math reasoning, Open-source deployment
Head-to-head aggregate scores
Scores are 0–100, aggregated from public benchmark information and independently weighted across three leaderboards. Rank is out of 22 tracked models.
Aggregated from public sources and independently weighted; methodology on the Terms page. Scores within 3 points are treated as statistically tied.
Specs & pricing — every field side by side
List API prices in USD per 1M tokens. The highlighted cell is the stronger value/capability on that row.
| Dimension | GPT-5.5 | DeepSeek-V4-Pro | Verdict |
|---|---|---|---|
| Vendor | OpenAI (US) | DeepSeek (CN) | Different vendors |
| Released | 2026.04 | 2026.04 | DeepSeek-V4-Pro is newer |
| Overall (rank) | 81 · #5 | 77 · #8 | GPT-5.5 +4 |
| Coding | 75 · #8 | 79 · #5 | DeepSeek-V4-Pro +4 |
| Multimodal | 85 · #8 | 77 · #13 | GPT-5.5 +8 |
| Context window | 1.05M | 1M | GPT-5.5 larger |
| Max output | 128K | 128K | Tie |
| Effective-context | 90 | 94 | DeepSeek-V4-Pro more reliable |
| Input $/1M | $5 | $0.44 | DeepSeek-V4-Pro cheaper |
| Output $/1M | $30 | $1.32 | DeepSeek-V4-Pro cheaper |
| Cache discount | 50% off | none | GPT-5.5 deeper |
| Speed | ~50 tok/s | ~70 tok/s | DeepSeek-V4-Pro faster |
| TTFT | 0.8s | 0.5s | DeepSeek-V4-Pro snappier |
| Function calling | 95 | 82 | GPT-5.5 ahead |
| Refusal rate | ~15% | ~5% | DeepSeek-V4-Pro less restrictive |
| English | 94 | 82 | GPT-5.5 |
| Chinese | 76 | 85 | DeepSeek-V4-Pro |
| Modalities | text, image | text | different coverage |
| Open weights | No | Yes | DeepSeek-V4-Pro is open |
| Fine-tuning | Yes | Yes | |
| Free tier | ChatGPT free tier available (rate-limited); Plus $20/month | DeepSeek App free; new API users receive credits | |
| SOC2 / no-train | yes / yes | no / yes | |
| Private deployment | No | Yes | DeepSeek-V4-Pro |
Fields drawn from vendor public documentation and the Modelspectra 22-model dataset; speed varies with network, concurrency and prompt length. Verify current pricing before purchase.
Dimension-by-dimension analysis
Reasoning & overall intelligence
GPT-5.5 leads the overall aggregate by 4 points (81 vs 77). That is a meaningful, not marginal, edge on hard, multi-step reasoning, while DeepSeek-V4-Pro remains a strong generalist that is not out of its depth on routine work.
Agentic coding
This is a modest gap: DeepSeek-V4-Pro scores 79 against 75. On multi-file edits, SWE-style tickets and long-horizon agent loops DeepSeek-V4-Pro needs fewer correction turns; GPT-5.5 is still competent for scripts and assisted completion but trails as task complexity rises.
Multimodal
GPT-5.5 leads multimodal 85 vs 77. A concrete modality difference: GPT-5.5 additionally handles image. Neither emits native video, so the comparison is about parsing images and documents, not generation.
Speed & latency
DeepSeek-V4-Pro is faster in interactive use: ~70 tok/s with 0.5s TTFT versus ~50 tok/s with 0.8s TTFT (about 1.4× the throughput). For conversational UIs where perceived responsiveness drives retention, that edge is a real product factor even when raw reasoning is lower.
Context: window vs usable recall
Nominal windows are 1.05M for GPT-5.5 and 1M for DeepSeek-V4-Pro. Crucially, the larger nominal window does not win on usable recall: GPT-5.5 advertises 1.05M but DeepSeek-V4-Pro scores higher on effective-context (94 vs 90), i.e. it actually retains more of what it was given.
Price & total cost
DeepSeek-V4-Pro is the cheaper API at $0.44/$1.32 versus GPT-5.5 at $5/$30 per 1M input/output tokens — list input is about 11.4× lower. Cache discounts (GPT-5.5 50%) shift the effective bill, worked out below.
Chinese vs English
English: GPT-5.5 94 vs DeepSeek-V4-Pro 82. Chinese: 76 vs 85. For Chinese-language production, DeepSeek-V4-Pro is the stronger pick. Note that non-Chinese models generally require overseas network access for their APIs.
Tool use & ecosystem
Function-calling score: GPT-5.5 95 vs DeepSeek-V4-Pro 82, so GPT-5.5 has the edge on structured tool use. Fine-tuning is available from GPT-5.5 and DeepSeek-V4-Pro. Factor in existing SDK/plugin familiarity — switching cost often outweighs a few-point tool-use gap.
Cost worked example — same workload, real token math
Assume a production workload of 100M input + 30M output tokens per month, with 90% of input tokens served from cache. Figures use public list prices.
| Scenario · per month | GPT-5.5 | DeepSeek-V4-Pro | Gap |
|---|---|---|---|
| List priceno cache applied | $1,400100M in × $5 + 30M out × $30 | $84100M in × $0.44 + 30M out × $1.32 | 16.67×gap |
| With caching90% of inputs cache-hit | $1,17590M cached in × $2.5 + 10M in × $5 + 30M out × $30 | $84no published cache discount | 13.99×gap |
Illustrative model; your input/output mix and cache-hit ratio change the result. Prices are list rates before any enterprise agreement.