For offroad, you gain nothing. Actually in some sense you lose something. What happens is when the suspension compresses on a standard suspension, the leaf has to move forward in the direction of motion. This puts more pressure down on that side and gives the tires more traction.
Onroad the SRS's are supposed to be nice because they allow more movement. Although, if you have bumpsteer, you'll have a lot more because the suspension will be softer. I haven't driven a SRS equiped Jeep but if it's softer then my SOA, it's gonna be scary. You also have to worry about driveshaft length in that the shaft may be too short when the suspension moves. Probably used to wat the MORE Buggy setup but that's pretty much stopped. If I was going to get one, I'd go with the standard setup. Not all kits will give you lift either. The ones that don't usually require welding. Actually, in either case, welding would probably be a good idea.
So, if you're looking for more lift, there are better ways. Oh, BTW: the SRS's lift is like a shackle lift which changes the pinion angle, for better or worse. :nothing: