I believe the 1080 has a more expensive and better construction, which makes it stiffer too.
The 720 is really flimsy, looks pretty cheap.
The 540 looks reeeeally flimsy, but its not made for most of us on this board.
I think all of Salomons skis this years look good, the 1080s, 720, 540, crossmax, xscream pilot etc.