i store my consoles in those plastic sweater boxes with cables and such. When i watch the Angry Video Game Nerd hooking up an Atari5200 with all those systems hooked-up at once, i scream "FIRE HAZZARD!" it freaks me out.
i hook mine up, play, when i want to switch, it goes back in it's box, onto the plastic etagere and then the other one gets hooked up. I even trained my son, who would want to play one system, then a different one, then...smack! one system at a time!
so, BOTH
(but Sega Genesis is my fave)