Z4: fast and smooth. This car did not have sport seats and I absolutely could not imagine owning this car without them. I was sliding all over, gripping the wheel to stay put. There are different sounds than in the 135. Same engine, different sensations. More turbo whistle in the 135, more intake and wastegate sound in the Z4. Handling was great, but hard to tell the limits in those seats. I can imagine this particular car as a great cruiser for two. This car had the 7 speed double clutch gearbox. I would normally never pick ANY car without a third pedal, but this one is good. For the average driver, they could never tell it wasn't a true automatic transmission. In Sport + mode, it was awesome. I like the cruise control on this better because it has the +5 mph feature. The 135 doesn't for some unknown reason.

135: Faster and firmer. This car has the sport package and the feel after immediately jumping out of the Z4 was intense. The seats grip like a vise, the road is like reading braille. The Z4 was a loaner while the 135 was in the shop for a bent rim. I 'broke in' the 135, so I know why it is faster. It also has 2000 miles on it vs. 500 in the Z4. This car makes me want to drive, even top up in the winter! Plus it is less expensive and has a back seat. Sold.