The F-35 can get "there" faster. The A-10 can hang out longer and carry a larger load. The A-10 can take a lot of punishment. The F-35 is harder to see and target electronically, and faster passes give less time to act on visual sighting. The A-10's slower passes allow the pilot to see and recognize targets better. The A-10 carries a lot more of the heavier 30 mm cannon shells than does the F-35 and its 25 mm cannon.
Were I a boot on the ground I'd want both to be available and AH-64s as well. If the desk drivers really are thinking in an either-or paradigm I think they need to get out in the real battlefield.