Koni has a recent development (at least for Class C's) called FSD for Frequency Sensitive Dampening. Those are the ones I'd read about. Cost is about 2x a Bilstein.
Disclaimer: I do NOT have those installed. I base this on many reviews here and promotion of the FSD's at Hendersons Line Up near you in Grants Pass OR. Our crew here has had only good to report about FSD.
I left the computer and a couple votes came in for Bilstein. That's a Name that Needs no Introduction, anywhere in the world, and a great product.
What FSD is supposed to do, is probably more noticeable in the rear. Guys who have them, jump in if I'm wrong. E450 rear axle just pounds its way down the road, every expansion joint. Then you hit The Big One and want your shocks to react to it and control movement. Both brands'll do that. What FSD does, is de-emphasize its response to that constant high speed drumming by not being as tight as on a big bump. Frequency Sensitive = Majoring on the Major.
I ended up with two new Ford shocks on the front because they came with a new axle I bought. I have old Brand ??? on the rear. Might just spring for a pair of FSD's for that end... If I needed all four... sure tempting to buy four Bilstein for the price of two FSD...