The biggest advantage of facegen (for me) is that it works also for newly generated players, custom leagues and for lower level leagues that don't have facepacks for them. I like to "get personal" with my players (however weird that sounds) and to see their faces.
No offense, but I don't really care if the faces are real or not (especially fictional and new players
). Real pictures are better but they don't work everywhere and that's where I would like to use facegen (even with hats).
I even think I've read somewhere that facegen causes young players look young and they get older as the time goes. If this is right I find it pretty cool. Another possibilities like playoff beards are beyond cool
Just my 2 cents.