The two aren't really comparable at all because of the vast differences in flex characteristics of the boot/binding combos. I would tell you what I think of Sidewinders, but it is not relevant to this discussion. Personally I don't see a need for hinge in softboot bindings at all, because of the greater range of motion of the ankle. Unless your binding was as stiff as hardboots. It looks like yours is not.
A softboot binding that could provide hardboot-type support and performance would have to basically be a hardboot that bolts to the board and opens up like a clamshell to let your softboot in and out. I think Flow bindings are closest to this. Make the tongue rigid, taller, and wrap around more and voila. As for a 3-strap binding, I think making one to equal hardboots will turn out looking much beefier, more enclosed, and nothing like the binding you've got going.
However for ultimate carving and racing performance, hardboots will always be the choice.
It's been done in Rollerblades, if that matters. Real freeride snowboarders spend way more of their day riding than walking, so I personally can't really fathom buying boots with walking as a criterion. Unless we're talking backcountry or hiking a pipe or a jump over and over. The only time I am sick of having my hardboots on is in the apres-ski bar with the onset of swamp-foot, and then I just take the boots off.