Here's the deal with Famicoms...
Original Famicom - ONLY RF output unless you mod it. And Japanese TV stations don't line up perfectly with US stations, so on most US TVs the picture will be not great because the signal is slightly off. Controllers are built-in with really short cords, but it has an accessory port for 3rd party controllers and things like lightguns (which you'd have to import as well). Will not support US accessories at all without some custom-made adapter. Has the coolest design, IMO.
AV Famicom - Only AV output, using the same cable as the SNES, N64, and GCN. Has regular NES controller ports (originally came with dogbone controllers) as well as the Japanese accessory port. Accepts most US accessories (things like US lightguns and multi-taps don't work on Famicom games, because the Japanese equivalents are programmed differently, but anything that acts like a regular controller will work, like the Advantage or NES Maxes). These ports come at a price, though, which is the loss of the microphone otherwise found in the player 2 controller. Only a handful of games used it, but it's still worth noting. Casing just looks like a top-loader NES with a flat top.
Sharp Twin Famicom & Sharp Twin Turbo - Has both RF and AV out. Controllers are built in, but has longer cords than the original Famicom. Twin Turbo's cords are even longer still and has rapid fire functions built in. Has the Japanese accessory port, no NES-type controller ports. These are the way to go for functionality, but they just don't look as cool, IMO. Not that looks really matter.
The belts aren't any more/less reliable on the Sharp Twins than on a regular FDS. In fact, if you open up either Twin model, you'll find they've basically taken the guts of a Famicom and the guts of a FDS and set them next to each other.
As for electricity... Because of the whole post-WW2 occupation thing, Japanese outlets are essentially the same as American outlets... were before we started including the ground pin and polarized plugs (left one being larger than the right). So Japanese electronics will plug in in the US just fine. There IS a slight difference in the voltage (theirs are 100V, while ours are 120V), and some people (not unwisely) use step-down converters for running Japanese electronics/appliances in the US... But most don't and have no problem. The system may run a little hotter than it's supposed to, but not enough to cause damage.
HOWEVER the MOST IMPORTANT thing about electricity and the Famicom is
DO NOT USE AN NES'S POWER SUPPLY WITH THE FAMICOM! EVER!!! The plug on the system's end is the same, but the Famicom converts the electricity from AC to DC in the cord, while the NES does it in the system itself. You give the Famicom AC when it's expecting DC and it'll fry!
As for where to buy, I don't know. I got my Famicom while on vacation in Japan. I will advise caution on importing FDS games, because there were kiosks that would write a new game over a game you already have (or onto a blank disk), so sometimes you might buy (for example) a disk that was and is still labeled as The Legend of Zelda only to find that it's Wrecking Crew. Or Othelo.
