GPT-5.3 Codex vs. Claude Opus 4.6: Which Coding Assistant Should New Developers Choose?

This hands-on comparison tests GPT-5.3 Codex and Claude Opus 4.6 across app building, debugging, and architectural review to determine which AI coding assistant better supports beginner developers. Codex prioritizes speed and momentum, while Claude emphasizes structured planning and reasoning. The best choice depends on whether you value rapid execution or deeper engineering clarity.