I have M3 + V8 X5 with the new M performance package (tune + exhaust from factory). That X5 is an absolute monster, so much pull and one of meanest V8 exhaust I've heard stock. I read on the X5 boards that it sounds better than the X5M. Having already an M car I didn't see the need to have an M SUV, so I saved a lot of $ and still have a very fast X5. It's also not a problem to get an extra winter wheel+tire set for the X5.
2015 M3 6MT | Yas Marina Blue, CF Roof, Cloth | Adaptive M Susp, 437M 19" Silver | Stripper
2013 X5 xDrive50i | Carbon Black | M Sport + M Perf, 333M | Loaded