I have/had both impact vests. I also use the Dakine seat harness. I rode the Dakine Surface vest for about 6 months ago until I lost it. Then I decided to try something different so I ordered the Promotion Vest this past year. I like both. I can confirm that the Dakine Surface vest offers a bit more protection and is slightly bulkier. In fact, I felt like Lou Ferrigno when I wore it, which isn't a bad thing. The advantage of the Promotion vest is the velcro, which offers a bit more flexibility and adjustability. There is also a zipped pocket in the back which I may use one day. Im going on a trip with 2 newbies, and I suggested the Dakine vest for them, as they were available and they seem to offer a bit more protection and perhaps floatation.
I didn't have a problem with either riding up, but sizing more important with the Dakine. Im 5'8, 170 lbs, 39 chest. I originally got a large surface vest, but latter switched to a medium. This is because the large felt better in the store, however, the vest loosens up when it gets wet, so the medium was the right size, plus the neoprene stretches. I would guess the large should fit you fine. I do believe the large did ride up a bit when it got loose, but not much. Both vests are thin on the bottom, so both seat and waist harnesses fit around them easy. In fact, it makes the harness more comfortable.
I do wish the promotion offered a bit more protection along the sides, but the Surface vest could have used more protection on the sides also. They both help with hard slams regardless, along with providing some floatation which make self rescue or even water relaunching easier. Overall, Im pleased with the promotion, they make gear suited for kiters. I made other purchases from them and plan on buying future wetsuits, etc.
My take on a vest is that its only useful if you wear it. Both are easy to get into because of the front zippers. While there are other vests that offer more protection and buoyancy, they also tend to be more restriction, making me less inclined to wear them consistently. Overall, I'd give a slight edge to promotion because of the velcro that allows for more flexibility (for instance if Im wearing a wetsuit). Hope this helps.