If you wanna sift through some tech, look on TTORA for the coilover thread. It's old, from the DR days, but I suspect Icon is using the same valving from when they were working for Donahoe. There's a lot of tech from DR and SAW (IIRC) on the thread.
The really short version is DR was using digressive valving (probably still is, call Icon and ask, they're good guys), SAW is probably using valving adopted from Camburg which is most likely linear, call Burg and ask for Scott or call SAW and ask for Ryan. If you call any of those guys, let 'em know you came over from TundraSolutions, Icon is a forum sponsor, SAW and Burg are on the forums as well and at least Burg has considered becoming a forum sponsor in the past.
The bottom line is, you're going to get a very, very nice coilover either way, with excellent valving and top shelf customer service, and unless you're really flogging the hell out of it--which is a little dubious with a 6" lift--you're not gonna really notice any valving difference other than they're probably valved better than the 5100s you have now.
So pick a color

...give any of those guys a call if you have questions, they all know each other and they're all really helpful.
-Sean