What are "clip on" bars? I have seen a couple people mention that, but I've never seen a bar that just clips on. Of the two sets I have on my bikes, they clamp on to the regular bars, but they're bolted down. I don't know how you could have some that just clip on.
Anyway, I have just started calling them "ergo" bars. As stated in my post above, I use them to reduce muscle fatigue in my arms. I would prefer the elbow pads to be a little further out than most bars allow for, but like I said, I'm not using them to reduce aerodynamic drag (at <20mph pace, how much aerodynamic drag to I really have anyway?). Ultimately, I do think they make me faster, but as a result of less fatigue. Not any "aero" advantage.