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Anthropic: Claude Sonnet 4.6 vs OpenAI: GPT-5.3-Codex: Coding Performance with 10 Evaluators

We put Anthropic: Claude Sonnet 4.6 and OpenAI: GPT-5.3-Codex to the test in a rigorous Coding Performance with 10 Evaluators benchmarking suite.

Anthropic: Claude Sonnet 4.6

5.5

preference score

vs

OpenAI: GPT-5.3-Codex

4.5

preference score

Judges ranked the responses in this Run against each other; the rank is mapped onto a 0–10 scale. It shows which response was preferred, not how good either one is — and it is not a percentage, a pass rate, or a check that the output was correct.

Sample size for this comparison was not recorded. Treat it as directional.

Evidence clarification: this article predates recorded sample provenance. Treat its conclusions as claims about the displayed examples; they do not establish general model superiority, verified correctness, or production suitability.

Key Findings

Top PerformerAnthropic: Claude Sonnet 4.6

Achieved the highest overall score of 5.53 in our comparative coding benchmark.

Instruction AdherenceAnthropic: Claude Sonnet 4.6

Consistently ranked higher by human evaluators for following complex coding constraints.

Cost AdvantageOpenAI: GPT-5.3-Codex

Maintained a slightly lower total cost profile while providing higher completion token volume.

Specifications

SpecAnthropic: Claude Sonnet 4.6OpenAI: GPT-5.3-Codex
Provideranthropicopenai
Context Length1.0M400K
Input Price (per 1M tokens)$3.00$1.75
Output Price (per 1M tokens)$15.00$14.00
Max Output Tokens128,000128,000
Tierfrontierpremium

Our Verdict

Anthropic: Claude Sonnet 4.6 emerges as the clear winner for coding-intensive tasks, demonstrating superior accuracy and instruction-following capabilities. While OpenAI: GPT-5.3-Codex is a viable alternative for cost-sensitive, high-volume tasks, it currently trails behind in the quality of output as evaluated by our 10-person expert panel.

Overview

In the rapidly evolving landscape of AI-assisted development, choosing the right model is critical for productivity. This report provides an in-depth look at Anthropic: Claude Sonnet 4.6 vs OpenAI: GPT-5.3-Codex. Using PeerLM's comparative evaluation framework, we engaged 10 independent evaluators to rank these models based on their ability to handle real-world coding tasks. This benchmark focus on Coding Performance with 10 Evaluators highlights which model provides the most reliable logic and syntax generation.

Benchmark Results

The evaluation utilized a comparative ranking methodology, where models were pitted against each other to determine which provided superior code quality and instruction adherence. Below is the summary of the performance metrics observed during this run.

ModelOverall ScoreAccuracyInstruction Following
Anthropic: Claude Sonnet 4.65.535.535.53
OpenAI: GPT-5.3-Codex4.474.474.47

Criteria Breakdown

Our 10 evaluators focused on two primary pillars: Accuracy and Instruction Following. The comparative methodology reveals a distinct preference for the output generated by Claude Sonnet 4.6. By analyzing the 1.06 point score spread, it is clear that while both models are capable, the consistency of Claude Sonnet 4.6 in maintaining logical flow and adhering to complex coding constraints outperformed the GPT-5.3-Codex iteration in this specific suite.

Cost & Latency

Understanding the economic and performance trade-offs is vital for enterprise integration. While both models demonstrate comparable cost profiles, their efficiency differs slightly based on token distribution.

  • Anthropic: Claude Sonnet 4.6: Total cost of $0.014196 with an average of 189 completion tokens per response.
  • OpenAI: GPT-5.3-Codex: Total cost of $0.014091 with an average of 225 completion tokens per response.

While OpenAI: GPT-5.3-Codex is slightly more cost-effective per output token, Anthropic: Claude Sonnet 4.6 justifies its premium through higher accuracy scores as determined by our evaluators.

Use Cases

Anthropic: Claude Sonnet 4.6 is best suited for complex refactoring, architectural design, and high-stakes coding tasks where logical precision is paramount. Its ability to follow strict instructions makes it an ideal pair-programmer for enterprise-grade codebases.

OpenAI: GPT-5.3-Codex remains a highly competitive option, particularly for rapid prototyping and scenarios where higher token throughput per dollar is a priority. It performs well in standard boilerplate generation and straightforward scripting tasks.

Verdict

In the context of Coding Performance with 10 Evaluators, Anthropic: Claude Sonnet 4.6 is the superior choice for users demanding high accuracy and strict adherence to coding standards. While OpenAI: GPT-5.3-Codex offers a competitive cost structure, the performance gap in logical reasoning and instruction following positions Claude Sonnet 4.6 as the current leader for professional software development workflows.

Backed by real data

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Methodology

Evaluated using PeerLM's blind evaluation pipeline with 4 responses per model across 2 criteria.