Why does Rylais give 300 HP when Mallet gives 700?

Rylai's: 300 hp and 90 ap for 2600 gold Mallet: 700 hp and 30 ad for 3100 gold

Mallet offers less offensive stats and has a higher cost.

Mallet is for champs that want a lot of hp, and for its cost and stats, it is worse than rylais.

So this is your gripe for the whole eighth season? Please don't ask why; no one quite knows the reason. It could be perhaps that Morello's shoes are too tight. It could be that Ryze's head isn't screwed on just right. But I think that the most likely reason of all may be that one is meant for fighter/tanks, and one is meant for mages, and mages don't have much HP at all.