The higher seat probably wouldn't present a problem for static water fishing, but I would have to think that once you start navigating a moving waterway it could present a problem. The angler's center of gravity certainly is higher with that seat, although the effect may be lessened a bit by the wider platform of the boat.
I guess I'm a bit partial to my sit-on-top because that's what I learned to fly fish off of and it works well. I don't stand on mine although if I really wanted to I probably could. I just don't see the need to as the stealth mode offered by a kayak works wonders. Standing in a kayak just seems like a recipe for disaster to me particularly with trying to cast a fly rod. To each his own I suppose, but eventually the law of averages wins out and you're gonna go for a swim.
Neat to see all the new concepts for kayak fishing vessels hitting the market though. Tons of new ideas out there for this budding new area of fishing.