I'll give some input since I've run both setups.
We'll start with the bad. I couldn't remove my Superflex springs fast enough! I was NOT happy in the slightest with them, and they do NOT carry the weight they claim. Others have complained about the same about the same issues. If you plan on running Superflex spring with a rear bumper, and full size carrier. You better think about running airbags with them as well.
Now I'm running 861's with Tokico's, and couldn't be happier. The Tokico's will be stiffer than the Bilstein's, but if you're carrying weight that's not a bad thing. I'm now running 861's with a rear bumper, 285/75/16 spare, fold down table, jerry can, and a custom sleeping/storage platform with no issues.
If you don't plan on running weight the Superflex will be just fine. If you plan on getting a rear bumper, and all that than get the 861's.