Both, electric and hydraulic, have been around for many years. Historically electrics were used on lighter rigs such as towables with hydraulic focused on heavier applications. A few years back Atwood came out with a heavy duty electric set up that you can find on several models of 40' class A's but the trend appears to have reversed with hydraulics cornering the class A market once again.
Myself I install a Quadra Big Foot manual hydraulic system a few years back. System has been trouble free and I'm very satisfied. What I've always wondering about is why do the builders install the operator's panel in the driving area? I installed the panel near my slide controls mid coach. Jacks go down slides go out, slides come in jack go up.