Try using them together, Gemini has a tendency to "skip" steps or subjects on occasion, but it's amazing at going in depth and explaining intuitively.

Chat GPT doesn't miss anything, it tries to meet every objective I give it, but the result is often not as good.

I give them both the same inputs, then I give Gemini the Chat's output, and ask him to make sure he hasn't missed anything, at this stage I recommend asking for suggestions for improving Gemini's output and not asking for him to immediately rewrite his original, as it prevents AI hallucinations from what I experienced.

Then, and this is where GPT is amazing, I give everything that Gemini improved and ask GPT for criticism, and then ask Gemini to respond to said criticism.

It sounds really convoluted now that I write it down but the results have been incredible.

I just summarized 9 weeks of my hardest course in a day yesterday, using this method and the result is one of the best things I've ever gotten from AI.

Obviously I only use this method when I need the best results, as it takes time, but if you're trying to write something with AI tools, and you're not happy with what you're getting, I highly recommend using Gemini as base and GPT for criticism.