My brother recently bought a 370Z Nismo and tbh, it’s a cracking car. I wouldn’t swap my MC for one but if I was buying today I’d be very tempted to get one over an Z4M as it’s considerably newer and less highly strung.
The engine isn’t as ‘special’ as the S54 and is quite muted as standard. They can sound incredible with a couple of mods and personally, I prefer the natural sound of a V6 over the straight 6 unless you put an airbox on the S54.
Speed wise, there’s not much in it but the Z4M has the edge. Seats in the nismo are great and the general cabin feels well put together (possibly because it’s almost new with just 8k on the clocks, but it’s much better than a friends 350Z) which is an area I feel the Z4 is lacking somewhat-tbh, my girlfriends Z3 feels better screwed together than a Z4. It probably isn’t from a technical point of view but the perceived quality is way up imo.
Both cars are pretty stiff but bearably so. I haven’t driven the Nismo so can’t comment on feel or handling but my brother who is very in to track days and has a history of tuned, nimble French hot hatches, seems to be happy with it as a usable fun road car. YMMV on this as it’s a very subjective point.
Between the ‘standard’ Z4 and 370, I have no experience but from reading around, it seems the 370 is perhaps closer to the nismo than the 3.0 is to the Z4m
. Whatever the case may be, I wouldn’t listen to the fanboys on either side, go drive both and make your choice. These kind of cars are more about the experience than the raw numbers so buy on feel and go with what your heart wants.