Definitely go with a Model 1 if it's working. Like Jibbajaba said, they are worth more, plus they just look better if you already have a model 1 Genesis/MD. I would definitely check it out really well before buying it though if you can. I had a Model 1 that was constantly popping the tray out, and it was way more than just bad stretched belt. Luckily there are plenty of cheap broken model 1's around so I just swapped out the cd drive and all was well.
If you don't care about looks and want to probably have less of a hassle, just go with the model 2, but to me it just doesn't seem right.