I dont think that Gandalf would be able to control the ring for long, actually now that i think of it i think that Galadriel would be the most dangerous because she seems as though she could control it best. Maybe the ? should be rephrased........it should be.....If the ring could be controlled by anyone, who would have the greatest advantage over all other beings?
The Balrog is a Maia; has all the power it needs.
There is no sense in which Galadriel can 'control' the power of the Ring that Gandalf could not. Neither of them meant they would be taken over by it (as beings without power tend to be). Just the power they wielded with the Ring would, inevitably, turn to evil purpose- that is its nature.