Mario was already well-rounded in Brawl, but simply not up to par. He had notable disadvantages of mediocre KO moves, a poor recovery, and short range.
So to be improved, Mario ended up with a little of everything: Better fireballs for approaching, a better down tilt for matchups where he can combo, stronger KO moves for those where he can’t, a stronger forward air for off-stage offense, and a slightly improved recovery.
This should make him the versatile, well rounded character he always wanted to be.
Balanced Brawl Bonus: Super Walljump Punch
This change allows Mario to cancel his Super Jump Punch into a walljump. Unlike in Super Smash Brothers Melee, this cancel can be done at any time during the Super Jump Punch, not just at the apex of the jump.
Other Major Changes
Up smash, down smash, and back throw are all more powerful KO moves.