One thing to keep in mind: Not every model fits every stove. I have a Bobby Flay model somebody gave me, for instance, that doesn't fit my stovetop. So whatever you choose, make sure it will rest evenly across the burners. Most of them are intended to work with two burners at once.
Aluminum will be much lighter and rapid heating, but using High heat can permanently warp the unit. Cast on the other hand is heavy, but basically will last forever, using whatever heat level you choose.