Us old men greatly prefer 18's and even GASP consider a set of 17's as fall/winter tires.
Performance, price, braking (safety), rim protection, comfort.
Looks better to some (I actually prefer the "serious" look of a car with proper tires vs giant rims with O-rings on them).
Drive what makes you smile!
06 330i 6mt Spt- Eibach Springs, BMW Perf Susp, Supersprint Exhaust, BSW Audio
94 325i 5mt 4d- M3 springs/susp, Z3 wheels, Chipped, Intake, Exhaust= FUN!