Why not put Bilstein 20% all around?

Ok, I'm getting confused as to which Bilstein shocks I should get. And after doing a bit of search, I noticed people recommend the 5100 20% stiff in the front and OE in the back. Why is that? I understand the 20% in front is to help carry the extra weight of trucks with winch bumpers, but why not put 20% in the back as well so that when you go haul those bags of rock salt from Home Deopt, your truck don't sag.

Does the 20% stiff in the back make the ride too bumpy, loose, and harsh when there's no cargo in the back?

And how much of a difference are the Bilstein OE from the 20% stiff?

Thanks

Here's why: Your truck will sag just as much when heavily loaded, and will ride much harsher during the 99% of the time it spends unloaded. Shocks have NOTHING to do with sagging or ride height, that is strictly dictated by the springs.
The constant added mass of a bumper/winch combination needs both stiffer torsion bars to withstand the load without wearing out prematurely, and stiffer shocks to help dampen the added inertia of the heavier front end.

That said, I have 20% all around with only a fairly light TJM T17 bumper up front. I don't mind the stiffer ride, and I do like the improvement in overall vehicle stability they provide. When I have had my X heavily loaded on the trail (I sleep in my X so I carry all my gear around with me), it controls chassis motion quite well and others riding with me have remarked how smooth it was at speed on uneven gravel roads and such.

Brent

Also if you have your rear swaybar removed the 20% will help slightly with body roll.

Thanks for the feedback. I still have my sway bar in the back (I think) so I guess I'll go with the 20 in front and OE in the back that everyone recommends. Brent, I had no idea that sag depends on the springs and not the shocks. Thanks for clarifying that.

So has anyone found a cheaper place to buy bilsteins besides SLR?