I have never had the Hellwigs, but I did have others on my '97 Mountaineer before I put airbags on it. Anything that I put on it firmed up the ride some & helped with load capacity, but the rear would still sag with a load of PA & music equipment or with a trailer. I ended up with the airbags & the load controller, and I've been happy with it ever since. At least with the air bags, I can keep the rear higher than the front with a trailer attached so that I can have more steering control in bad weather. The only problem was that at the minimum 10 psi the rear is higher than the front by 1/2" stock, so I compensated with a torsion twist, and now I might have to reverse the trailer hitch drawbar to drop the ball height since I'm having problems driving the boat back onto the trailer even with the airbags at 5 psi as the low pressure sensor is currently set improperly to 5 psi.
If you don't plan to tow or haul a heavy load, the Hellwigs should be fine.