Practically the same. Both can be said interchangeably

As Chris said. I don't think these are interchangeable - I think the first one is wrong. You can't use "would have" after "wish" like this. The construction works with other verbs e.g. "I think I would have done it differently" or "I know I would have done it differently" but not with "wish". Why? Because "would" is a conditional and implies an "if" - "(given these conditions), I think I would have done it differently". However, "I wish" expresses a simple desire, without conditions, and this conflicts with the conditional in sentence 1.