You can compare it yourself. Try asking CoPilot "code review all the files in this project and tell me what it does and how to improve it". If it does something at the same level of usefulness as ChatGPT, then its equivalent. If it struggles ... then ChatGPT has an advantage.

I personally don't have a CoPilot license. But I do pay the $20/mo for ChatGPT and found that the way it can reason about code, even about a whole project, is just mind blowing.