It can depend on your venue as well. We are getting married outside, so it doesn't really make sense to just have the groomsmen standing up there already, and its a pretty long path. You'd understand if you saw it! So the groomsmen will walk the bridesmaids down the aisle. Even though they are not actual couples, I think its classy to have a girl escorted. And my bridesmaids who have been in weddings in the past, say they are much more comfortable walking with someone.
Our bridesmaids are walking alone and the groomsmen are coming from the front, meeting them in the middle of the aisle and walking the rest of the way with them.
I think I would find it awkward as a bridesmaid to have everyone staring at me as I walk down the aisle alone...
I think I am going to leave this one to my FI. He might feel more at ease if the guys are standing with him rather than just him and the officiant.
If he doesn't care, then I'd probably go for walking in pairs simply b/c I preferred that as a BM (i worried i'd fall or something and didn't like having so many eyes on just me....obv need to get past that for my wedding!)