I just installed a set of Bilstein HD's on our GM chassis 28QB. The one thing we noticed was the reduction of "porpoising". The OEM units had 16000 miles and seemed to still be okay, just not as capable of dampening as the new Bilsteins. Although I read that they are more harsh then the Koni's, I can't say that they added any harness to the ride on our unit.
As for holding up, it's my understanding Bilstein will rebuild them for you. We do have about 30k miles on a set on our Tahoe.
If your shocks are worn, I suspect either brand you mentioned should result in an improvement in ride and/or handling.
Gary