Keeping Marine Angelfish

Hi, I am looking into getting an angelfish for a large 250-300 gallon tank. I heard that you can only keep one angelfish per tank, if this is true i wanted to know out of a king/passer angelfish or a majestic/blue-griddled angelfish which one would be the easiest to keep?



If you have any tips on keeping these angelfish that would also be greatly appreciated.