5th wheel requires the plate style hitch with the rails that will take up half of your bed. Gooseneck is a 2 5/16" ball that is mounted in the floor of your bed and typically either folds down or pops up and retracts when you're not using it. My personal preference would be the gooseneck as you don't have to deal with a big bulky heavy hitch when you're not using the trailer. Besides, even with a 5th wheel style RV, there are quite a few companies that make conversion kits to put a gooseneck style hitch on to them. It's just much easier to deal with the gooseneck.
Just my $.02.