I installed the Firestone Ride Rites on my Class C unit a couple months ago. I had a couple reasons why, I was leaning to one side and not level front to back. My unit is a 1989 so it has some years on it. It was sagging to the point that the levelers wouldn't retract. After I got them installed I can level it both front to back and side to side, it made the ride better as well and feels more stable on the road. I can't comment on the Sumo springs since I have never been around them.
Rick and Mimi
1989 Class C Fleetwood Tioga, 26 ft on an E350 Frame
Toad: 2000 Dodge Dakota 4x4.