The 100 type film is the stuff made by Fuji. You can use the FP3000B and 100B B+W film and the FP100C film which is colour.
Both give superb results. I've had a few 'pack' cameras (a 104, 250, 450 and now a 195)
I highly recommend the metal bodied versions; they are beautiful and nicely made. They don't cost much more than the plastic ones either.
The only differences to really worry about are the flash and the timer.
The flash for the 450 required 'Hi-Power' flashcubes which aren't so easy to come by. Having said that, with the 3000 speed film you won't use it often. I found a huge case of cubes on eBay and really enjoyed the flash.
The other cameras use M3 flashbulb jobs that look great, produce a lovely 'Hollywood' style light and are easy to find bulbs for.
The timer is the other concern. On the back of the body there's sometimes, depending on the model, a digital timer or a clockwork one or none at all. You don't need a timer; the Fuji stuff develops in 30 seconds and stops, so you can peel them apart a while after you take the shot. The digital timer requires batteries to operate and it makes the back of the camera a bit fatter leaving less room for the fuji film packs, which for some reason are slightly thicker than the original Polaroid ones.
Because of this, I recommend the 250 as the best 'consumer' model - it's metal, has no timer and has a nice Zeiss finder (RF and framelines in one window). Make sure yours comes with the #268 flash.
The 'best' models are arguably the 'pro' versions, the 180, 185, 190 and 195. These had really nice lenses (f3.8 on the 195 I have, equivalent of f1.4 on 35mm), and they are fully manual and therefore batteryless. It may not be quite as convenient as the automatic exposure on something like the 250 in every situation, however, but the lens is just beautiful.
Hope that ramble helps - I say get a good 250 and some FP300B film and go for it.
I'll be selling some accessories soon (close up kit, portrait kit, UV and cloud filters) as the 195 has different threads etc so look out of them!
Cheers
ped