I have a tall regular on my 05 GasGas and it is very plush. The seat is no higher in the back, just the center. Creates a very flat riding surface. I also had a tall regular on my KTM and that was also plush. The reason I went to a firm on the KTM is the comfort seat is only offered in standard height. On the KTM I wanted the different shape and at standard height the foam is thin. I didn't want to feel the seat base if the foam was soft. On Guts web site they describe the firmness of the various foams by descibing stock seats of different brands and from my experience it is a good reference.
Sorry for all the KTM references......