Practicing for the FTD is definitely smart, but I don't think you have to get too crazy about it. I just used Microsoft Flight Sim with a yoke and was fine. If you have easy access to a Frasca, then great! But I wouldn't waste several hundred dollars on prep (unless you are very rusty).

Regarding who gets picked, I agree it just all depends. I had previous 135 experience and a fresh part 91 type on a jet. The first thing I did was the sim! Others in my group did it, some didn't. More than anything else it just seemed to be a function of how much time was available to fit everything in.