The big reason for going to the Lippert slide mechanisms is the fact that they take up less than 1/2 the space of the HWH hydraulic units. The motors don't physically have to be large because they use gear reduction to produce the torque needed to extend and retract the slides.
We had HWH on our old coach and they weren't exactly trouble free. The main slide needed 3 cylinders to make it move. There was 1 on each end providing in and out motion and a larger 1 in the middle used to equalize hydraulic pressure so the ones on the end operated in a coordinated manner. All in all there was close to 100 lbs. of cylinders and almost 50' of hydraulic lines to power 1 slide.
The Lippert system takes up less space, weighs less than 1/4 of what the HWH system did, requires less infrastructure. There's also no hydraulic fluid to leak on the floor or the ground. Also if there are problems the motors and slide mechanisms can be replaced without disassembling half the slide.
The downsides are that it takes a fair amount of skill to install and adjust properly and it needs an almost fully charged battery to extend and retract full wall slides. I think these types of mechanisms are going to stay around.
