I think it's a simple thing...
If you're going to tow or carry heavy loads, get the Z71.
If you want all the lift you can get, get the Z71s.
If you don't have either need, stay stock.
I tow from time-to-time, and generally have a few hundred pounds of stuff in the boot. Plus, I don't mind some extra clearance under the petrol tank. So, I like em.
FYI, to answer an earlier post... old GM trucks had solid front axles... 2WD solid axle trucks can be lower in front because they don't need clearance for the diff / driveshaft... 4WD solid axle trucks are jacked a bit more to accommodate those things.