I think that had this been the 90's, beardless would be the way to go. However, the beard is back lately, so I think a well groomed beard would be acceptable.
If you're going to grow a beard, go big or go home. The only way to impress an adcom is with innovative engineering, similar to this man: http://www.collegehumor.com/video:1924916. This fellow has a full cage around his head along with a real working door made completely out of beard hair. If your beard can't successfully house a bird, you're merely disheveled.
I grow a decent beard but since I work in a Fire Based EMS its a blanket policy on beards, Shave ( Even the women😀).
To me though I think their are far an few folks that you walk in an they say " I see 4.0gpa MCAT 45 Saved Kittens From Burning Tree, Cured Cancer and World Hunger, No Beard well Im sorry but good day sir, I SAID GOOD DAY SIR!😱.