Same context class, different home
Both Sonnet 5 and Gemini 3 Pro advertise million-token windows. Claude’s coding agents are more mature (Claude Code). Gemini’s advantage is Vertex, Workspace, and Antigravity if you are already in that campus.
Price
Gemini 3 Pro is $1.50 / $6 versus Sonnet 5 at $2 / $10. Flash SKUs undercut both for autocomplete. If output tokens dominate, Gemini’s list price is the cheaper Google-native option.