The primary reason I have switched is that creative writing has plummeted on ChatGPT. It is overly eager to censor output that isn't adult but might vaguely be adult if taken incorrectly. This severely limits creative freedom. On the other hand, Gemini happily writes my stories.

I am not sure who OpenAI aims to please by nerfing their own product in this way. It can't be paying customers.

there was that teen who died after chat supposedly encouraged him to do bad things and his parents are suing now. so maybe more controls are being put in place to reduce risk.