I cringe when I see someone put Ketchup on a Hot Dog, but I am a native New Yorker. I hear they perform that sacrilege in Chicago though. I'm sure it's one of Obama’s favorites, like Marxism.
Mayonnaise can and should go on both.
Oh, man. Hot dogs have got to be deluxe. Mustard, catsup, relish, onion, Spanish sauce, and if you must cheese. I’m not a cheese person, but a hot dog deluxe must have cheese here in the Midwest.