well team grav is the best because we can not be stopped.
got a shield we will use momentum past it
got a creature our oty will eat it
got a really big creature slap up a gravity shield and call it dead weight.
also we can borrow some cards from earth like pulverize and enchant artifact without sacrificing any of our power to stop you from destroying our stuff and destroy your stuff at the same time. so watch out for the gravity time power