Don't get me wrong - I like Minis, but they are more overpriced than the 500 in my view.
Hmm. Remember the Mini is (probably) built from better quality components, has cheaper servicing & may have better residuals - I'd say that just about evens things up, leaving both cars similarly overpriced. But that's just my opinion & I suspect how well someone does in practice with either car is down to whether you get a good one or a lemon.
Best perhaps just to go for the one you like best - if it were all about the money, you'd likely buy something else entirely.