Koni’s or Bilsteins

Koni's are fine shocks but more than a little bit overpriced for what you get. I have had great results with the heavy duty Bilsteins {replaced the original shocks at 33K miles and now have 53K} on my 2012 E-350, 24' Class C.

I recently added Air Lift 5K# airbags to deal with a heavy tongue weight motorcycle trailer and was pleasantly surprised at the ride improvement when running lite with just 15-20 psi vs the 50# I run when towing. Between the Bilestins and the airbags a ride I always considered to be excellent just got better.

Be advised that installing Bilsteins is a serious PITA and not recommended for DIY.

:C

I run an underloaded E450 with 14,500 gross and I sit on a scale at 12,500 all fully loaded.
Needless to say, my 450 back end pounded on bumps. The following set up did help on the good advice on our one of our members here and I'm happy with it.
I did Koni FSD in the rear and Bils up front and a Supersteer rear track bar which BTW was the best upgrade I did for wind. That track bar really helped with crosswinds and bow waves from big trucks. A good positive caster alignment really helped as well. My rig really rides nice now.
I really don't know if doing Bils on all 4 would make much difference , I think I would try Bils all around if I was trying to save money.
My next spring upgrade will be air bags with an on board compressor in order to gain 2" of ground clearance when needed, I drag my hitch on aprons of driveways more often than I like.
The key is that the track bar has to set at normal riding level in order for peak performance. Full bags will be too high a ride for normal travel but will do what I need for short bursts into driveways and hilly campgrounds.