Well, now that I have been to two sets of dunes, I can say it depends on the sand and type of riding. There were people out at dumont with some tires called mini desert paddle or something like that and they were smokin. They did awesome. V-paddles were working good out there to. The sand wasn't really really soft, but it started getting softer as the weekend went.
I know that's not an answer and I don't think anyone can give you the perfect answer. Depends were you want your strongest point.. sliding, duning without a giant roost, dragging, just cruising. Seemed to me every paddle had it's goods and bad.