He can in fact jump higher than Mario - and slow his descent like Yoshi can.
AND he's taller and more athletic than Mario. And he's also Stronger too.
The only handicap that I see is that he's a bit of a Coward and a little too shy. Instead of barging into Danger Head-First like his brother, he's more than willing to hang back and let Mario take point.
"harness the power of thunder and lightning"....
Jeesh that makes Luigi sound EPIC!!! I never thought of it that way!
...Or maybe they're both just taking pity on the PlayStation. That works too.