You mention a Cooper, presumably you mean a Cooper S.
Cooper S can be tuned to the max and are insane in a way more "fun" way than any BMW. If it floats your boat, go for it. I regularly see some very nice Cooper S's, sometimes even Works edition, they can be very nice with the richt colors/options. A hoot to drive.
If you actually meant Cooper, then do not buy a Cooper, buy a ONE and have it tuned. The engine in the Cooper and the ONE are EXACTLY the same, the HP difference is an engine management thing.