I've seen a bit of everything...and here's what I've noticed.
I'm going with about 6" of lift here in my examples.
Short arms and no drop brackets = harsh ride and limited flex...BTDT
Short arms and drop brackets = much better ride, way better flex, BTDT.
Now, anything smaller (that I've seen) than 35s with drop brackets the brackets may become an issue as far as rock hangups go. On the other hand...longarm kits that are mounted on the UNDERSIDE of the frame with ANY size tire hang up like crazy! I've seen them hang up way more than anything...and I didn't like what I saw. However, I've wheeled with/ridden in another rig where the guy took RE TJ longarms when they first came out and built his OWN crossmember for them to fit. Only difference is he mounted them INBOARD and UP in such a way that if you look at it from the side you CANNOT see the arms!!! THIS way virtually eliminates all hangups that I mentioned before. He's riding on 37s and Bilstein 9100's. The ride? I've not felt a better ride in a Cadillac. Does that say much? I think it does.
In all my conclusion would be that for the $$, you're better off with short arms and drop brackets. Unless you're going to do the longarms RIGHT, don't waste your time mounting them under the frame.