If you are allowed to use the fast track facilities, I find the access located on the AirLink's side always quicker compared to the other one which, on a recent visit before the first morning service to Frankfurt, was not even manned. That said, I fly out of Birmingham on a weekly basis and the standard access points always seem to look pretty busy, incidentally the other day it took me over 5 minutes to actually get to the right lane as people were queuing just as I stepped out of the AirLink (it didn't help that there was a good number of people trying to get to the people mover).
G