The free tier handles casual use well. Paid plans add GPT-5 access, Deep Research, the Codex agent, and much higher usage limits. If AI is part of your daily workflow, the time savings tend to quickly pay for the subscription.

Set up custom instructions with your role and output preferences first. Then use Projects to keep related chats organized and turn on memory so context carries over between sessions. For anything research-heavy, switch to Deep Research — the results are noticeably more thorough than a standard chat.

Codex handles writing, debugging, and PR prep well. For deep IDE-native workflows or repo-wide refactoring, dedicated tools like Cursor or Claude Code may be a better fit. ChatGPT's edge is that coding, research, and writing all live in the same tool.

ChatGPT lets you choose between different reasoning levels, ranging from Instant (fastest responses) to Pro Extended (deepest reasoning). You can also let ChatGPT select the most appropriate option automatically — using faster models for simple questions and more advanced reasoning for complex tasks. The available models and reasoning options depend on your subscription plan.

ChatGPT is broader: web search, image gen, custom GPTs, a huge plugin ecosystem. Claude is sharper on long-form writing, careful instruction-following, and extended coding tasks. A lot of professionals use both and route each task to whichever handles it better.