(omg) You HAVE to drive them before you compare.
The Z is awesome, but you will see what I mean about the "heavy" feeling. And as far as the 8 goes, make SURE to revv it high. It's much like my miata, very high RPM hp (if you've never driven a rotary before), so keeping the revvs up is key. You won't feel a sudden rush of hp like the boosted MSP, but trust me, before you know it, you will be soaring beyond the speed limit. I LOVE it.
You can't go wrong with the Mini either, from what I have heard from owners. I have yet to test drive one as well.