American Snowmobiler Mag did a Real Word Shootout in March. Pretty interesting results. The sleds tested that apply to the thread were a MXZ XRS 800 etec, a SR Viper and a Viper LTX SE. Several other sleds were also tested. The Doo was faster and quicker in almost every category except the 0-30 in which the SR Viper was .01 seconds quicker. The Doo was 1.47 secs and the SR Viper was 1.46 secs for the 0-30 run. The Viper LTX was 1.57 secs.
Time to 660 feet was: Doo 7.71 secs (89.60 mph), SR Viper 8.26 secs (78.67 mph) and Viper LTX was 8.09 secs (83.36 mph).
Looking at all the times, speeds and distances, it appears the SR Viper has a great hole shot, then after 30 mph, the 800 etec pulls away...according to this test on this day with these stock sleds anyway.
This test was done with all sleds on the same course with the same driver. Also, over 350 miles were put on all the sleds prior to the testing which is not done during the Old Forge Shootout American Snowmobiler does every December. It is work a read just as more information.
You might have to be a magazine suscriber to read the whole article just as an FYI.
http://www.amsnow.com/Subscriber Extras/Shootout Results/2014/03/2014 Real World Shootout.aspx