Yeah, but +2 str, -2 dex and the benefits for large combined will give you this:
+0 to attack (+1 str, -1 size) and -2 AC (-1 dex, -1 size). +1-3 damage on average (+1 str, +1-2 if weapon size increases). +4 grapple, trip, bull rush's, etc.
So the biggest draw is the +1-3 damage and reach...