I started off with the small version, as it was cheaper and I worried the large one would be too big and get hooked on branches all the time. Surprisingly I have found the opposite to be true, the small one is fairly weak and as there is not a great deal of tension in the sprung clip I found it was forever clipping itself to branches, usually at the most inopportune moment! This frequently led to it snapping or the clip popping off.
After going through 3 or 4 of these in the space of a few months, I decided to try the large Caritool, hoping its heavier weight rating would also mean it was slightly more robust. I have been proved right, and have yet to break one, despite nearly 2 years worth of use. Which for £12ish is pretty damn good.
It also has a stronger clip, meaning branches are less likely to clip themselves in (it still happens, but not nearly as often!)
I have mine attached to the right hand side of my harness, just off centre from my hip, I use it exclusively for clipping my saw up and have developed a technique to do this one handed, quickly and easily (more on this when I do a post about my saw strop)
As stated before its robust, well made and currently standing the test of time, putting up with considerable abuse and must have been clipped into thousands of times by now. My main criticisms are firstly that I'd happily trade some weight gain for a solid gate rather than wire, as you'd be amazed how frequently tiny little branches can wedge themselves inside the wire gate!
My second criticism is one that I have in part managed to solve and its probably more to do with compatibility to my harness than anything else, but I found that it would often turn its self upside down or move around the harness webbing, or slide upwards and the little clip wasn't really sufficient to keep it in place.
I solved this with the addition of a strip of tire inner tube, cut to twice the width of the harness webbing and with two slits, centred and cut slightly further apart than one width of webbing, the caritool is then poked through one slit, into the harness and the other end stretched and round the caritool, the two ends of the rubber then get folded round the back of the harness strap and hopefully everything then stays happily in place
Hopefully the pictures explain it better than my ramblings