The Soire design requires you to us to a plastic Unift adapter, so the flush is not straight down. The Unift adapter, with its curved shape, would seem to be a cause for potenial clogs over the long term. Plus, you need to put 2 extra screw holes in the back of your floor to hold down the adapter....versus using only 2 bolts to connect the toilet to the drain flange. Plus, the weight of the toilet on the seal is not straight down either. It seems to me a straight down seal with the bowl weight on top of it is much less likely to leak over time, versus the Soiree design with a back seal that is cantilevered to the main drain flange seal.
Seems like I would be better off with a more standard design to replace my 39 yaer old 4/5 gallon Kohler Wellington. My Kohler has the bolts to the drain flange at about 13 inches from the back wall, so there is plenty of room.