I have 1 of each both with aftermarket ekholm tunnels with drop and roll chain cases and 9 tooth extrovert drivers, srx is a 141 and viper is 144,I just bought and rebuilt srx last year and barely have 10 miles on it, viper just bought last month and rebuilding motor, i could tell a huge difference over my 121 99 srx, seems like they lift out of the snow better instead of digging a trench on takeoff