Vo benchmarks both models using her ChatPRD marketing site, redesigning it for enterprise customers rather than PLG users. While Codex excels at precise code review, architectural analysis, and Git-integrated workflows—especially with features like work trees and scheduled automations—it struggles with creative, open-ended tasks due to overly literal prompt interpretation and limited self-editing. In contrast, Opus 4.6 shines in generative, long-horizon development: it successfully refactored gnarly components, rebuilt key pages with brand-aligned visuals, and enabled rapid iteration toward production-ready output. Together, they form a complementary stack—Opus handling ideation and implementation, Codex ensuring correctness and polish. This synergy powered a massive engineering sprint: 44 PRs, 98 commits, and over 1,000 files touched in five days. Vo also cautions about cost trade-offs, noting Opus 4.6 Fast delivers speed but demands careful token budgeting.