I have not used either but in researching different ones, I found this ... I hope that helps
Quoted from http://www.poolsupplyworld.com/pools...OOLROVERJR.htm
"regarding the differences between the Aquabot Pool Rover Jr. and the Aquabot Pool Rover Hybrid.

The Pool Rover Jr. is designed for above ground, flat bottom pools, while the Pool Rover Hybrid is designed for bowl-shaped above ground pools (with inclines up to 30 degrees), but can also be used with in-ground pools.

The Hybrid cleans pools up to 40' in one hour, while the Pool Rover Jr. cleans pools up to 30' in 30 minutes. Both cleaners filter down to 2 microns, operate at 24V, have a 19 quart capacity filter bag and include a 40' non-corroding Kevlar power cable."