i heard they do effect how effective a player is but is it like a player with 50 str & 272 lbs will have the same "in-game" strength as someone with 45 str & 330 lbs... just curious cause i never cared about that!
Taller means a higher center of gravity, which in GLB means "easier to topple". Think pancakes or even tackles. But for WRs and defense means higher reach. Heavier means tougher to tackle and push around. Lighter means higher acceleration.
So if your a linemen you'd want short heavy guys; for WR and coverage tall light ones. But this is just normal a OT wont be 190lb while your CB might be.
There was a discussion thread about this with a Bort apperance sometime last season. Still the official reasonning is that it matters but not much.