The German Cats were always breaking down. Tanks do not operate in a vacuum. Under a very specific set of circumstances they were better. That being purely defensive, not having to cross any bridges, not having to be transported by rail, not having to perform road marches, and not having to have quick maintenance done on the road wheels.
Even when the M-26 was about as reliable as the Panther, the War Department would not release the M-26 into ETO as being unfit for combat.