I regularly carry a SF L1 and C2 on my belt. I find that although the short clip of the L1 has bit bit stronger/firmer of a grip, it isn't long enough to go completely over the belt, so it tends to get knocked off more easily than the C2. By contrast, the C2 is more easily knocked out of position (sliding forward or back, or even slightly up and towards getting un-clipped), but it almost never does so without being easily noticed and rectified. So, the short clip may stay put more often, but when it moves, it's much more likely to fall off the belt altogether. (I keep both lights on lanyards, tethered to a belt loop, just in case.)
Basically, if the clip seems sufficiently sturdy, and it's long enough to clear the belt fully, then I'd be comfortable clipping the light to my belt (even without a tether). If, however, it's too short for that, then I'll still clip it to the belt for convenience, but only if it's tethered to me so I don't lose it.