My knowledge on these two systems is fairly limited... I know the SMS is region free (At least between the US and Europe) and it plays cartridges AND cards, and I know that the Game Gear drains batteries like there's no tomorrow (So I'm getting a wall cord for it, or whatever you call it, to use instead of batteries). I know the Game Gear screen is kind of small, and I know the SMS can also use Genesis controllers.
But is there anything important I don't know (i.e. "Sometimes you have to twist the plug in a 180 degree circle to get it to work")? I only know about the NES on up. Any help, even if you think it's stupid, would be appreciated. What might seem stupid or simple to you may be something I don't know.
Thanks for your help!