If anybody has noticed, I'm definitely one of the biggest Bilal supporters on this site, but that's a hard topic to choose sides on. And it really is hard to compare the two considering how little most of us have heard of Bilal, but here goes (By the way, I'm the farthest thing from a music genius, so forgive my lack of knowledge. This is gonna be mostly opinion-driven. I'm not an expert.):

Bilal (from what I've heard):
Strong voice and wide range
(From what I've heard) writes, produces, and plays several intruments.
Easy to understand
Cool artistic look (shell glasses and hat)
Is a modern funky soul brotha (always a plus)

D'Angelo:
Thick soulful voice and smooth falsetto
Genius writing, producing, and intrumentation
Hard to understand, but voice powerful enough to make it not matter
Cool artisitic look (making cornrows popular)
Modern funky soul brotha PIMP!

Okay, my lists did me absolutely no good, so now I have to wait for either someone to make a better one, or for Bilal's album to drop so I can make a better comparison. Okay, bottom line: they're both equally good artists in their own rights, so we should respect them equally for their talents. How's that? Love and respect.
-B