I was shocked to see the shoot out results from AM Snow...Polaris won both the 600, and 800 shoot out...even though the 800 polaris is less HP than the Doo or Cat 800.....the viper/cat was right there with the fast 600's in 1000 ft....they didn't test the nytro...but I suspect they would be faster than the viper /cat... the new exhaust, and cat's efi calibrations put the viper at 130 HP...which is where it is advertised at...it's more similar with the vector, than it is with the nytro (nytro dyno's range from 136-138 HP).
I have two friends with 2013 switchback rush's...I have not ridden them yet....but they LOVE them.....one is a 600...and it is an over achiver....it is faster than his 700 dragon switchback to 90 MPH!!!.....the 800 is also very quick....they both love the handling....the only thing they hate....is even with taller windshields...both guys said they are cold machines in colder weather.
You can pick on the 4 stokes for weight ...and sometimes handling...the engines are awesome (especially the yamaha's)....I had nearly 14,000 miles on my attak...the engine was flawless...however...bushings.. bearings, and other basic maintnance items are no different than any other sled....having owned all 4 brands over the last 20 years...all of them have their glitches.....but...there is NO COMPARISON engine wise 4 strokes have far less maintenance....and run far more consistant than 2 strokes...I had ZERO worries with the engine in my attak...could not say the same about a few of my two strokes.
IMO...It's a trade off...you get more weight, but you gain reliability, and durability