I like the back inflation style with a hard plate...Hollis, Dive Rite and the like. I never liked the vest style in cold water. I dive a Dive Rite Trans plate with a Venture wing and love it. It is stable and comfortable. I dove it in FL a couple of months ago...first warm water dive... and even over a 3 mm suit it was still comfortable. I think this style is the most versitile.
Steve