Giant Rat is faster, but it is also very risky to run it. You need 3x Giant Rats, because sometimes it happens you opponent has already 2~3 monsters summoned and need to summon rat..rat..Hootcake. However in that case you have already one monster too much in your graveyard. Well that shouldn't hurt a normal Madolche player since he does not use the majority of the madolche trap cards which force you to have no monsters in your graveyard in order for them to work. But if you have so much graveyard control with Key Mouse, you can even add a Madolche Pundingcess to your deck, because you can really make use of her. Of course in that case you would lose your Gian Rat wall, but you won't need that thing if you just add 3x Waboku and 3x Threatening Roar. Thats right, Key Mouse can not be special summoned, but if you have 3x Double Summon, 1x Ultimate Offering and 1x Madolche Happy Festa your problem is solved. And this guys also give you more speed.