I love AI Studio. It's free to use and you can switch between models. Gemini 2.5 Pro's reasoning can be a little slow so if you don't need it you can switch to Gemini 2.0 Flash (which is capable of 100-200 tokens per second). You can even switch between models later. The only downside of using it over the user-facing Gemini web app is that you need to save your chats.