I've used all three, so here's my comparison.
ChatGPT: Fastest and best at understanding conversation context. But sometimes it's overly polite, which can be a bit annoying lol.
Claude: Best for creative writing or scenario work. Rich and emotional sentences. Downside: Korean support is still incomplete.
Gemini: The advantage is integration with the Google ecosystem. Great for YouTube summaries or search assistance, but reasoning ability is slightly lacking.
Conclusion: It seems best to choose based on the situation. I use GPT for coding, Claude for writing, and Gemini for searches.