I can't see any of these recommendations being duffers but some have characteristics which may be more important to you personally, e.g. wear, noise, comfort, ultimate wet weather performance over dry etc. At the end of the day it's a compromise but any of them will do an excellent job and the differences are quite subjective really.
IMO tyre reviews are not that helpful as they usually test it on a car with very different characteristics to the Z4 so I've gone with tyres recommended by members twice now (Falken 452 now Eagle F1A2) and have not regretted the advice.