Timbrens are like adding overload springs in that they do nothing till a load is applied. By that time the headlights are slightly elevated and I would get a lot of flashing lights coming the other way. With the air bags you remain level, there is a difference in ride performance a little more bounce in the rear empty but not uncomfortable. It would be nice to find a couple of friends with either so you could feel the difference before buying, personally I will stick with the air bags.
Hope this helps
Rich and Marita