Weirdly, if you're already holding an EVIL Miscreant (which you want) it's not necessarily a terrible idea to keep hold of Togwaggle, especially if you think it'll be a slower match up. Other than that card draw - always card draw.
Anything to try and keep the board clear.
If it's Mage, it'll be Cyclone/Conjurer ... in which case you're probably going to want ways to remove big things, Wild Pyromancer, Plaguebringer and a cheap spell will completely clear the board - or Walk the Plank for a single Giant before it's hit with Conjurer's Calling.
Remember you'll need one Walk the Plank to kill Mecha'thun at the end otherwise it'll be a matter of just smacking your opponent in the face with him and hoping they don't have Polymorph!