RE: Which Sim Should I Buy?
If your hobby shop is big enough, they'll have two sim demos setup. And chances are good that those two will be the only sims in stock.
Try them both and pick which one you like best.
As for what everyone would suggest, look through the threads here. The subject has been covered a number of times. And everything has been said that there is to say.
BTW, there is an AFPD forum here too. It's part of this one. Go back one step and you'll see it's link.