It's a different driving experience, both are awesome cars. The Z was a lot more playful on the limit whereas the M3 will bite, however once all the upgrades are on chassis wise it should surpass the Z, I will see how the M3 reacts to trail braking once the 8 pots are on but that's one thing the Z was great at, not getting out of shape to much when trail braking. The M3 is quite a bit quicker and a lot more repsonsive but that's a given seeing the Z has one throttle body and the M3 six and also the sport button (even sharper response once pressed), the brakes on the Z have much better stopping power, feel wise to but the M3 I find has better initial bite, I'm sure those attributes will change when the M3's new brakes are on and I do the rears aswell in the not to distant future. Comfort wise i like both, the cabin on the Z nice and snug and the HSD's did ride nicely, but the KW V3 on the M3 are a different league in terms on quality and ride comfort, the M3 cabin obviously much more spacious aswell with much nicer fit and finish overall. Sound wise I love both I mean what car guy doesn't, the Z was more exhaust noise and sounded really exotic whereas the M3 is more intake noise and sounds like a real racer, I love the distinctive rasp of the M to, so if I had to pick what sounded better overall taking into account intake and exhaust I'd pick the M3 but the exhaust noise alone the Z wins just, only down to the setup I had on it. M3 exhaust isn't finished yet so that decision may change once on. Both are blinding cars and I'm thankful I've owned both, I would love to get back into a Z at some point but it would have to be a supercharged HR in that bright orange.
If you've finished reading well done haha