-- Last Updated: Mar-17-13 6:57 PM EST --
I don't know the Riot. The seat system you would find in a Tsunami is hard to beat (though I usually do add another 3/8 of medium foam, under the seat cover). I think you're referring to the WS thigh lift, that is adjusted with straps. Yes, that can be very effective in combatting tingling toes that some paddlers get. And, while the Tsunamis do not come with hip pads, they can be added:
http://www.harmonygear.com/products/9678/Hip-Pad-Kit.html
Also, the Tsunami comes with a medium-high seat back that mounts to the seat pan. As you may get to where you want to learn more skills -- especially rolling -- you can swap out the seat back for a back band. It looks like less, but, it's really more:
http://www.harmonygear.com/products/9828/Dagger-Backband.html
(this has been available with the WS logo, and for less money; can't find it, currently)