I think many including myself opt for the sidewinder since it runs so much smoother than the viper. Rode my father in laws 11 vector this weekend and it is silky smooth like a sidewinder compared to the viper. Viper just never had that precision smoothness like every other yamaha 4 stroke sled. Initially I thought it was the driveline/chassis, but when sidewinder came out it quickly eliminated that theory because it ran so smooth just like the apex, vector, nytro models. This year we ran a sidewinder muffler on a viper and it helped smooth and quiet the sled down some more, but still not on level of sidewinder. Only thing left really is the ECU and electronic package, so really hoping if the Viper gets power steering it gets new electronics.