This poll should maybe say "What bike do you WISH to have?".... it's funny how you buy something and then later learn what might work better or what does work better.
I have the WR450 and I think it's a good bike.... it's not perfect but it's good and obviously I have a lot of fun on it. Estart, headlight, ability to put it on the road in the off season, etc. It has a lot of positives.
What bike do I want? The 2011 or 2012 KX450 (and I have one coming! YES!). The bike makes it's power in such a way that it just rips for a snowbike application. EFI is a major plus since you don't have to mess with the carb crap, which I hate and I really suck at. Add the Bazzaz AFR tuner and a FMF Powerbomb full exhaust.... can't be beat and I've yet to see any bike touch the all around nimbleness mixed with raw power that the KX450 has. Add to it Allen's good point that you can start the bike by hand and the Estart looks pointless. Another interesting point, with the Bazzaz tuner the fuel economy is just STUPID!!!! You can put an entire day in for only 2gal of gas sometimes while I'll go through 5gal on my Yamaha. Seriously.... a FULL DAY RIDE for only $8.00? That pays for the kit by itself over couple years!
KX450 is probably the best snowbike available.