o3-pro vs GPT-5.3 Codex
Head-to-head specifications
| Metric | o3-pro | GPT-5.3 Codex | Difference |
|---|---|---|---|
| Intelligence Index | 33.0 | 44.0 | -25.0% |
| Context window | 258K tokens | 922K tokens | — |
| Blended price ($/1M tokens) | $1.87 | $1.05 | +78.1% |
| Output speed (tokens/s) | 42 | 85 | -50.6% |
| Access | Proprietary API | Proprietary API | — |
- GPT-5.3 Codex leads overall capability (Intelligence Index 44.0 vs 33.0).
- GPT-5.3 Codex is the cheaper model to run at $1.05/1M blended tokens — about 1.8× cheaper.
- GPT-5.3 Codex offers the larger context window (922K tokens), useful for long documents and codebases.
Verdict: o3-pro or GPT-5.3 Codex?
o3-pro advantages
- No decisive advantage on the tracked metrics.
GPT-5.3 Codex advantages
- General intelligence (+25%)
- Context window (+72%)
- Affordability (+44%)
- Output speed (+51%)
Which should you choose?
- Choose the GPT-5.3 Codex if you need the strongest overall reasoning and accuracy.
Value for money
GPT-5.3 Codex offers more intelligence per dollar (2.4× the Intelligence-Index-per-cost of the alternative), making it the stronger value for high-volume use.
o3-pro vs GPT-5.3 Codex: which should you choose?
o3-pro — OpenAI multimodal model with an Intelligence Index of 33, a 258K-token context window and a blended price of $1.87/1M tokens.
GPT-5.3 Codex — OpenAI multimodal model with an Intelligence Index of 44, a 922K-token context window and a blended price of $1.05/1M tokens.
o3-pro vs GPT-5.3 Codex: GPT-5.3 Codex scores higher on the Intelligence Index. GPT-5.3 Codex leads overall capability (Intelligence Index 44.0 vs 33.0). GPT-5.3 Codex is the cheaper model to run at $1.05/1M blended tokens — about 1.8× cheaper.
Capability: intelligence, coding and agentic work
On the composite Intelligence Index the GPT-5.3 Codex scores 44.0 versus 33.0. Composite indices summarize many evaluations, but always test on your own workload before committing.
Context window and speed
The GPT-5.3 Codex accepts up to 922K tokens per request, which sets how much documentation, transcript or code it can reason over at once. In measured throughput, GPT-5.3 Codex generates faster (85 vs 42 tokens/s), which matters for interactive apps and high-volume pipelines.
Pricing and access
At blended per-token rates, GPT-5.3 Codex is the cheaper model to run ($1.05 vs $1.87 per 1M tokens). o3-pro is proprietary api and GPT-5.3 Codex is proprietary api. Open-weight models can be self-hosted, trading per-call cost for infrastructure you manage; for production also weigh rate limits, throughput and data-residency requirements.
The verdict
Both are credible choices in the ai model comparison space; the specification table above lays out every metric so you can weigh the trade-offs that matter to you. Pick the one whose strengths line up with how you will actually use it.
Frequently asked questions
Is the o3-pro better than the GPT-5.3 Codex?
GPT-5.3 Codex is the clearly stronger overall choice, winning most of the dimensions that matter. GPT-5.3 Codex leads overall capability (Intelligence Index 44.0 vs 33.0).
What is the main difference between the o3-pro and the GPT-5.3 Codex?
GPT-5.3 Codex leads overall capability (Intelligence Index 44.0 vs 33.0). GPT-5.3 Codex is the cheaper model to run at $1.05/1M blended tokens — about 1.8× cheaper.
Which is better value?
GPT-5.3 Codex offers more intelligence per dollar (2.4× the Intelligence-Index-per-cost of the alternative), making it the stronger value for high-volume use.
Which should I choose?
Choose the GPT-5.3 Codex if you need the strongest overall reasoning and accuracy.
Methodology
Large language models are compared on independent leaderboard metrics: an Intelligence Index (a composite of reasoning and knowledge evaluations), Coding and Agentic indices where measured, community arena Elo, maximum context window, a blended API price per million tokens (weighted across cache-hit, input and output rates), and measured output speed in tokens per second. Where a model ships multiple reasoning-effort variants, we report its strongest variant. Benchmarks capture only part of real-world quality, which also depends on tool use, latency, safety and task fit — and this space moves quickly, so figures reflect the leaderboard snapshot on the page date.