GPT-5.4 is the broader platform: 50% cheaper API ($2.50/$15 vs $5/$25 per MTok), native multimodal (DALL-E images, Sora video, Advanced Voice), polished computer use (OSWorld: 75.0%), and stronger performance on novel engineering problems (SWE-Bench Pro: 57.7% vs ~46%). Claude Opus 4.6 is the deeper specialist: #1 on standard coding (SWE-Bench Verified: 80.8%), #1 on abstract reasoning (ARC-AGI-2: 68.8% vs ~35%), #1 on terminal operations (Terminal-Bench 2.0: 65.4%), #1 on user satisfaction (Chatbot Arena), plus unique capabilities like Agent Teams, context compaction, and adaptive thinking. Choose ChatGPT if you need a do-everything assistant at lower cost. Choose Claude if coding depth, agent orchestration, reasoning, and writing quality are your priorities.