I've read several times that a 50mm lens will make features like noses noticeably stand out compared to an 85mm lens. However, I'm never sure if the post/article is describing results on a full frame or crop sensor. I know that the longer the focal length, the more the compression to features....because the crop sensor gives a 50mm a longer focal length, how noticeable is the facial distortion on say, a Canon 550D? I'm considering a prime for portrait work and I'm 'at the crossroads' like all of you who came before me ;)
EDIT I will generally be using the lens for wedding portraits on the beach (and they generally want to get married around sunset, so formal portraits come as I'm losing light---hence wanting a tack sharp f1.8 or below), so it would be handy to have a lens that can take more than just a head/shoulder shot.