ChatGPT. No point in adding an expensive middleman on top that’s usually just a few clever prompt tricks.
Side note: having gotten access to Copilot Chat, it’s disturbing how quickly the ChatGPT UI has become established in my mind as the standard. Copilot Chat, despite being integrated into VS Code, feels clunky and alien compared to ChatGPT in a separate window. Funny how fast new things become the standard by which others are measured.