I own both the Revolution and the Viper. For pure comfort, the Revolution is far and away the best. Having said that, the Viper is plenty comfortable and I can sit in it all day.

The one draw back I have found with the Revolution is it is not as easy to climb with. I realize Summit says it is a stand up sit down type of climber, but I found it almost impossible to use it the way they said. I use it as a hand climber, and the seat tends to get in the way a little bit. Having said that, I love mine and it is now my prefered climber. I will sacrifice a little flexibility in climbing for the additional comfort. However, many did not like the way it climbed engouh to trade it back in.

Either stand is great.