Quick Answer
Gemini has the largest context (2M tokens). Claude has the best-quality long context (200K).
Detailed Answer
For within-conversation memory: Gemini offers 2M tokens (can analyze entire codebases), Claude offers 200K tokens with better retention quality, ChatGPT offers 128K. For cross-conversation memory: ChatGPT has a "memory" feature that remembers facts between chats. Claude has "Projects" for persistent context. Different kinds of "memory" for different needs.
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