I greatly prefer the ND767a to the SM58 and Beta 58. Having had all of the above (and a few Sennheisers as well), I now have all vocals in the band on ND767a's.
The one place that I still prefer the SM58 is for singers with bad technique. For singers who swing their head all around and wave the mic at varying distances from their mouth, the broader pickup pattern of the SM58 is nicer.
The tighter pickup pattern of the ND767a (and others with super/hyper cardioid patterns) generally gives them greater resistance to feedback, but requires that you stay on the mic more consistently.
Microphones are like hair styles though. It is hard for everyone to agree on which one is the best.
