I have both installed on my 2014 Forest River Sierra 5th wheel bought new by me - 43' long, hitch weight 2900#, RV weight loaded 16,000#. I tow it with a 2018 Ford F-350 dually 6.7L diesel. we are full-timers travelling extensively throughout the US and Canada.
The trailair hitch assembly (air bag + shock) really reduces the "chucking". The level of chucking is highly dependent upon the road surface. Even with this hitch assembly, transitions from asphalt to concrete surfaces, frost heaves, and pot holes, can still be felt but not close to being as severe without a cushioning hitch. In my opinion, the cushioning effect of the hitch reduces strain on the chassis of the 5th wheel. Monitoring with the rear view mirror in the truck, I can see the rig's nose moving up and down on rougher roads. With a solid hitch, those shocks are administered directly to the 5th wheel chassis.
I have the MoRyde SRE4000 suspension on the rig as well. The MoRyde system has much more robust sprint hangers and spring equalizers than the stock suspension, plus a reinforcing cross member from the spring equalizer points. The greasable bolts and bronze bushings are much more robust. I had this installed on my rig at about 4K miles. The stock nylon bushings for the spring bolts were pretty much shredded and worn out.
I've since put about 60K miles on the rig (with the trailair hitch and MoRyde. Check everything out several times a year - no problems at all. In my opinion they are well worth the expense.