Hi, Cyn. A lot depends on your location and weather. It seems to me that the potential for plumbing problems is pretty high with both types. You would then have a choice of having your water line freeze coming into your house and having water ruin your ceiling and floor when a pipe leaks with pier and beam or having to dig up the concrete to fix a leak with a slab.
Personally, I prefer a full basement or could live with a slab. Save the post and beam for your deck.