I have ran all of these boats and I would have to side with PMGoff on this. I owned a 96 ProCraft, a 99, 2000, and 2001 Nitro, a 2002 Skeeter and have PLENTY of seat time in a few different models of Ranger (esp the 520).
They all have their pros and cons and for overall value and fishability I would pick a Nitro. For quality and resale, I would pick a Ranger. For speed and performance in flat to meduim water and a close second in fishability I would certainly rather have a Skeeter. A close second to Nitro in value and a little better quality would be the ProCraft.
It really boils down to the same things...how much you want to spend, what kind of motor you want to have, how are you going to use the boat and last, but certainly not least, where you can get quality service if needed. Your dealer will ultimately be your decision along with the money you want to spend.