Crooked Bee
(no longer) a wide-wandering bee
Saying "D:OS can be steamrolled hence its mechanics are not sound" is just retarded, so I won't even comment on that.
Which has to do with its encounter design. The mechanics are just standard D&D stuff that may or may not work depending on the encounter design; in KotC's case, it does, which is what makes it stand out -- not its mechanics.
KotC on the other hand is less flashy, but remains interesting throughout the duration of the entire game by forcing you to put thought into your build and how you approach each encounter.
Which has to do with its encounter design. The mechanics are just standard D&D stuff that may or may not work depending on the encounter design; in KotC's case, it does, which is what makes it stand out -- not its mechanics.