I have the same question. Sumo/Timbrens, or for ~$100 more timber grove airbags. I have a 24’ 10k car hauler. So far I’ve only towed it empty about 350 miles. It’s chatty but not overly so. No issues with big trucks (even in a tunnel - 2 lane oncoming traffic) but I haven’t experienced high cross winds yet. I have a wdh but have not configured it yet, will do that this weekend (hopefully -assuming i get the trailer back from warranty work) and since I expect to have the trailer close to max (hoping for 9k, maybe 9.5 max) I will set the hitch up with 1k of tongue weight (Just me, a bag for 3 days, a 50lb dog, and 10 gallons of gas in plastic Jerry cans in the bed - I will not be over gross!). In fact, I plan to scale the rig fully loaded so I can lay a fresh Cat scale report on Johnny Law should be decide i look like an easy mark.
I won’t really know how it’s going to tow fully loaded until I’m committed, and that has me nervous since committed means 2100 miles cross country with all my worldly possessions in the trailer. (1 bedroom set, sans mattress/box spring, and all the other household stuff, + motorcycle and tools.)
I’ll have a better idea once I have the wdh set up. And bags offer the most versatility over the springs. I do expect to do more towing after I’ve settled out west, but hopefully no where near gross again.
From what I’ve read, people who start out with sumo/timbren often wind up with bags anyway, I just no experience with either and I’m hoping those who do have something constructive to add..