Depends what you are benchmarking for... If you are benchmarking the ability of the solution to solve LEETCODE challenges, that is different to the ability of GPT4 to assist everyday programmers knock out business logic or diagnose bugs.
My experience of GPT4 is that it's significantly better at the latter than GPT3.5.
Additionally, the real test is for me is "Can an average programmer using GPT4 as a tool solve Advent of Code faster than an equally-skilled programmer without an LLM?".