Some people like the higher load carry capacity of a stiffer spring but not the additional height that comes with it. Some want that "leveled" look without having to go overboard lifting up the front end. Different strokes for different folks
Have you sat down and checked out this thread from front to back? http://www.toyota-4runner.org/5th-gen-t4rs/65893-post-your-lifted-pix-here.html
I highly suggest you first figure out how much total lift you personally want to go with and if you want to "level" out the rake; then starting thinking about what specific springs to get.
Basically, you don't want to first settle on a 3" rear spring only to realize you want to also level out the rake because you're going to end up with the front end having to be waaaaay to high up to level it. Same goes for the other way around, you don't want to end up with only a 1" rear spring only to realize that you want to keep the rake, then you won't be able to raise the front that much, lol.
Once you have that basic idea down, then you can start comparing spring rates and heights to fit your application better. Like [MENTION=74569]SOcalTRAIL[/MENTION] said, it all depends on what heavy add-ons you plan to have on the truck. Great example is, while his rear springs only give him ~2-3" lift, if you took his rear springs and put it on a stock truck, it will probably end up with a 4-5" lift, lol.
If I recall correctly, I think most of the OME rear springs are all a bit on the stiffer side, so if you like the softer plush ride, you should probably stick to another brand. They might feel a bit too stiff for some unless you like it like that, or if you plan to have a lot of constant weight in the rear.
I have the Sway-A-Way rear coils (like a lot of guys here) and IMO, it's just right in stiffness and you end up with ~2" lift. Great spring for a truck without a heavy rear bumper and/or hefty cargo drawers.
