In my experience, what you get on Bing is quite different from what you get on ChatGTP.

I would prefer the free ChatGPT 3.5 over what I get on Bing because Bing counts down the responses and tends to give much shorter answers.

Here is an example for Bing Chat vs ChatGPT Plus: https://dropover.cloud/4e1dd7

If you don't plan to use it enough to worth $20 a month, you can purchase some API credits from OpenAI which don't expire and use it directly from their developer playground.

Actually, IIRC they will give you some free credit valid for some time when you create an account on their developer platform so you should be able to give it a try yourself.

Go to: https://platform.openai.com

Create a new free account, then head to the http://platform.openai.com/playground and try out ChatGPT with GPT-4(might be unavailable on free credit until you top-up some money) on their Chat interface.