USCG approved have a certain amount of flotation and hold you face up, laying slightly back. There is a test for this supervised by the USCG. Rider's vests, as I call them, do not have the same amount of flotation material and may not hold you in the semi-reclined position. USCG vests typically have to have a lot of foam in the upper chest area to accomplish the task. This reduces mobility across the chest.
I use the Launch vest from KD (also Blindside, Double Up and Wet Tech) and like it. Easier to ride with. I have a standard vest in the boat for compliance purposes. My kids all have USCG vests on while in the boat, but a Pro Ride vest on while riding under supervision.
LT (former) USCGR