TNRIVER...I tow a 6K dry 25 ft. Keystone Outback with an '08 Tundra 4X4 using a 1K/10K Equalizer...so we're pretty similar in set-ups.
I had Airlift 5000's installed on my truck for several reasons:
#1. To try to minimize some pretty horrible porpoising on some bad sections of concrete-paved highways we frequently travel. End result, while the bags helped somewhat, I found I needed to CORRECTLY adjust the Equalizer, carefully following the factory directions and doing careful measurements. That made ALL the difference in the world.
#2. Sometimes, even with the WD bars in place, it just settles the ride down on bad terrain and especially those bad "Bump Ahead" events you occasionally find on highways.
#3. To be able to tow/move the trailer without the weight distribution bars in place eg. negotiating tight corners and backing into tight campsites, traversing sharp/steep inclines, and getting into my drive without scraping the bottom of the hitch post on the pavement (high street crown + deep curb gutter + sharp driveway apron incline).
I consider them very useful, under certain circumstances.
Regards, BGood