GPT-4o vs Claude 3.5 Sonnet: Full Comparison

Key Takeaways

Two Titans, One Question

GPT-4o and Claude 3.5 Sonnet are the two most widely deployed frontier models for everyday tasks. Both offer excellent instruction-following, strong coding ability, and long context windows. But they have meaningfully different strengths that make one a better fit than the other depending on your use case.

GPT-4o is OpenAI's multimodal flagship, processing text, images, and audio natively. Claude 3.5 Sonnet is Anthropic's mid-tier workhorse. It is faster and cheaper than Opus while approaching its quality on most tasks. Both began as Foundation Models and are deployed as Instruct Models aligned to follow user instructions.

Coding Performance

On HumanEval, GPT-4o scores 90.2% and Claude 3.5 Sonnet scores 92.0%. In practice, both models excel at generating boilerplate, debugging, and code review. Claude has a slight edge for longer, more complex coding tasks where context management and file consistency matter.

For agentic coding, both perform well. Claude's instruction-following precision gives it an advantage in structured coding workflows. If you are building a coding assistant or IDE integration, Claude 3.5 Sonnet is often the preferred choice among developers.

Writing and Creative Tasks

Claude is widely regarded as the better writer. Its prose is more naturally varied, its tone more calibrated, and it tends to avoid the slightly corporate cadence that GPT-4o can sometimes produce. For long-form content, marketing copy, and creative writing, Claude's outputs typically require less editing.

GPT-4o holds its own on structured writing tasks. Business emails, technical documentation, and report generation benefit from its more formal style. It is also notably stronger for multilingual writing, with better coverage of non-English languages due to OpenAI's training data breadth.

Reasoning and Analysis

On MMLU (broad knowledge) and GPQA (graduate-level reasoning), GPT-4o scores 87.2% and 53.6% respectively. Claude 3.5 Sonnet scores 89.0% and 59.4%. For hard multi-step reasoning, Claude has a consistent edge. Its Chain of Thought reasoning is more methodical, and it shows lower hallucination rates on knowledge-intensive tasks.

If reasoning is your primary use case, consider upgrading to Claude 3.7 Sonnet with extended thinking enabled, or OpenAI's o4-mini. Both are purpose-built for deep reasoning and vastly outperform general-purpose models on hard problems.

Cost and Speed

GPT-4o charges $2.50/M input tokens and $10/M output tokens. Claude 3.5 Sonnet charges $3/M input and $15/M output. It is slightly more expensive but often worth it for quality-sensitive applications. Both stream responses quickly, though GPT-4o tends to have lower median latency.

For high-volume applications where cost is paramount, consider Claude 3.5 Haiku ($0.80/$4.00) or GPT-4o Mini ($0.15/$0.60). Both offer strong value at drastically lower prices.

The Verdict

Choose Claude 3.5 Sonnet for long-form writing, nuanced reasoning, complex coding tasks, and applications where instruction-following precision matters. Choose GPT-4o for multimodal use cases involving image and text, multilingual applications, tight latency requirements, and OpenAI ecosystem integrations.

The good news: both models are exceptional. The difference in most everyday tasks is marginal. The best choice is often determined by ecosystem fit rather than raw capability. Try both on your specific tasks using Keimodel and let your actual use case decide.