Gandalf vs Saruman hu is more powerful???

Im not too sure about this guys soo bear with me but ummm im not sure hu is more powerful gandalf in his grey form or Saruman coz it says that Gandalf is more wiser than Saruman and that the other 3 wizards wanted Gandalf to become the leader of the order of wizards but Saruman ended up becoming it and im just confused about how and why Gandalf didnt become the leader even tho the others thought it was best? and also Saruman being the white wizard or Saruman of many colours some how defeated the other three wizrads and gained there rods of power and also somehow gained the crowns of the nine kings too (idk if this made sense at all but umm the main question im asking is well hu is more powerful) gandalf or saruman???