The hippopotamus in the room
One remains active until it is depleted while the other disappears 1sec after 1 hit. http://i.imgur.com/GCZhZnX.jpg http://i.imgur.com/vaCcLbM.jpg Yas can easily rebuild his shield without sacrificing anything to improve it, while Malp on the other hand not only has to stay out of combat to have it back up, but will also have to pick multiple hp items in order to make it as proficient as yas' late game 510 dmg absorption.
Welfare passives like yasuo's arent fair for champs like malp who actually have to contribute to make their passive more effective, and has a risk such as staying out of combat. The only way to make this a fair playing field is by giving malp a free double crit passive on top of his passive, make his e a dash, and give him a couple of Japanese yelling quotes.
INB4 Yas main, "but muh teh 2 different champ."