At first the sliding tom arm seemed like an unnecessary feature until I tried putting 8'', 10'' and 12'' in front of me. The ability to just slide the toms towards me made my set-up so much easier than with regular L arms so I switched to these. If you haven't used it before, remember to pull it out and put the larger end in the ball clamp, it's just packaged like that to save space.
Also, if you have a regular L arm where you can slide the tom up and down the arm, it can affect the resonance of the tom but it seems like Sonor have found the sweet spot so you don't have to worry about that.