I ride an '06 YZ250 and really like it. Have not had it in "deep" powder yet so no comment in that department.
The motor is stock (but tired) with a Pro-Circuit pipe. As best I can tell from surfing around the internet it would be around 47 hp with fresh top end. Since it's getting a new piston this summer, I may put in a 295 kit (the same cost as a fuel controller for a FI 450, approx $600). This will fatten the power band and make it easier to chug around like a 450.
I ride with some KX450's and they do go better, but for me the fun factor of a two stroke is where it's at. If you are getting into snow bikes for maximum hp and hill climbing, you would be missing the point altogether. That's what my 280 hp Nytro is for.
http://www.eric-gorr.com/bigbore250.html
Some dyno info I found:
http://antithumper.700hp.com/gasserfly.html
Dyno Test Results
2007 Honda CRF 450R: 51.2HP@9,540 RPM. It has FMF pipe & Stage II cam.
2006 Yamaha YZ250: 47.5HP@8,530 RPM. It has a Bill's Pipe.
2001 KTM 380SX: 51HP@8,050 RPM. Tired engine. (55HP fresh?)
2000 Honda CR500: 58HP@6,400 RPM. Pro Circuit pipe & Boyesen reeds.
2008 Gas Gas EC300: 47.6HP@7,300 RPM. Bone stock. Bel-Ray MC1
-----------------------
YZ250F 36 HP@11,000 rpm, 20.1 ft-lbs torque
YZ250 46.4 HP@8,500 rpm, 30.6 ft-lbs torque
YZ450 54 HP@?? rpm, 34 ft-lbs torque
From MXA Magazine:
Q: HOW DOES THE 2011 YZ450F RUN ON THE DYNO?
A: Maximum horsepower was 53.88 ponies. That’s a healthy number, albeit less than what the KTM, Suzuki and Kawasaki make. Maximum torque was 33.95 foot-pounds. For comparison purposes, the 2011 CRF450 (34.36), RM-Z450 (34.77), KTM 450SXF (35.28) and KX450F (35.29) all produce more torque. The YZ450F did, however, beat the KTM 350SXF (33.95 foot-pounds to 27.34 foot-pounds).
-----------------------------
Q: HOW DOES IT RUN ON THE DYNO?
A: It (2012 KX450F) makes 55.50 horsepower at peak (the 2011 KX450F made 54.17). Best of all, it crested the 50-horsepower mark at 7400 rpm and stayed above that mark all the way to 10,200 rpm. That is an awesome spread of power. It makes more horsepower than the 2011 KX450F engine from 6200 rpm all the way to sign-off, but doesn’t really whip the 2011 KX450F bad until 8500 rpm—and by 9500 it is making three horsepower more.
http://motocrossactionmag.com/Main/News/MXAS-2012-KAWASAKI-KX450F-MOTOCROSS-TEST-AN-ENGINE-8331.aspx
Sorry for writing a book, guess I'm bored and it's raining outside today.
Cheers!
LG