In today's game of odd-matchups from spread offenses, the differences between the two are blurring.
I will say that I've watched a few old Horns games from the early and mid 90's recently, and I think we've consistently shot ourselves in the foot with tall, largely immobile, SS's that other teams consistently picked on (e.g., Gunn, Tre Thomas, Jackson and Brown). These guys looked great and could hit, but it wasn't worth what it cost us in missed tackles and ineffective coverages when we played good teams (note, they were great against the weakling teams, though).
I much prefer to see the shorter (5'9-5'11') Dakarai Pearson, Vasher, Geiggar sized guys who won't get outjuked and blown by in coverage at SS and FS. I think the staff has moved in the right direction.