I would like the DSTwo because after recently getting two DSi's (one for me, one for my friend), I'm looking to get the best Flash Cart for it's value. The DSTwo is pretty amazing.
Unlike the iPlayer, it doubles as a multimedia device and as a backup cart. The XVid/DivX sounds great and if it supports h264 that'll be even better. It's processing power is pretty great, and if it's as good or better than the iPlayer it alone is more powerful than the DS with it's ARM SOC.
It's SOC will be amazing if an SDK is released publically because then I'd be able to code up on it too without being hindered by the DSi's TERRIBLE processing power and RAM.
Winning this will save me $34.50 as I will only have to buy one when it is released.