Of course it made us a better team, if nothing more than letting us keep players from getting tired going both ways. Adonis has been a big part of that defense....probably not as big if he had to play both ways. Also opens up the player to a bigger chance to getting an injury. And as far as comparing them at RB, Both are great but I think Calvin has more breakaway speed so I doubt Adonis would have as many long runs, which keeps the defense in a position to stop the drive. Now the flip side to that would be with Adonis running the ball and not getting those big runs the offense would eat more clock and he just downright punishes the defense setting them up to tire out.
As far as qb I can't really say a lot as I don't know who would have played there or know enough from for a comparison.