Jzero, you were in a Christian A Cappella group in college? So was I! My college had this one group that was sort of an institution at the school - not a school-sponsored group, but they had been going for ten years or so, changing out singers all the time when people graduated. My friend and I tried to get in, but there wasn't any room, so we started our own group. We wrote our own music and arranged many songs for ourselves. Ah, the memories

I sang bass on most songs, but took second tenor (melody) on at least two of our songs (I figured out in college that I have a four and a half octave range).
Now I sing in church every Sunday. I just bought this new guitar (Taylor 614ce), and I generally sing the melody parts to help lead the congregation, but sometimes harmonizing. On perormance songs (as opposed to congregational songs) I generally sing the lead part if it's a guy's part.
And I agree to a point on the bigger guy, higher voice theory. I'm 6'7", about 300 lbs, and I sing high sometimes, but I also have a lower voice than anyone else that I've ever sang with. I generally sing bass on most songs (I was second bass, which is the low bass, in choir in college).