damn i had a good thread going a while back comparing harris, caldwell, blackhawk, "rock mount", and the champion branded stuff. got lost in the site switchover. i did not use the utg version
the harris is definately more upscale with the finish, the quality of the hardware used, the spring and it's tension, and the mechanisms for deploying the legs. of the "harris styled stuff" the original is still the most solid, and if you can spend the extra on it, it's worth it.
i'd put the caldwell over the other "knockoffs" i've tried. it's not as upscale as the harris, but IMO not as far off as the others.
the blackhawk, champion, and rock mount brands a bit more flimsy, less spring tension, flexy legs. they work, and will do the job at the range, but would depend on a more solid bipod with the caldwell or harris over them.
then comes height - if prone i like the 9"-13" range for prone, for bench the 6-9", and in the field the tall 13-27" pivoting for odd positions and for sitting on uneven terrain. in the field, i usually have the tall one mounted, and keep the 9-13" in the pack and switch them if the set up calls for it.
then the next consideration is legs - notched or smooth - for hunting i like the idea of getting in the general area quicker via leg notches, but prefer the smooth to adjust to the sweet spot when at the range.
some of the versions have legs that spring out and you have to push in, some have the pull out, hit the button, and they collapse. harris has pull out collapse with button, i think caldwell has the spring out style. i forget how the blackhawk and the rock mount ones operate. i prefer the pull out for if you are setting up and have to make an adjustment, the whole rig doesn't fall down if you lose your grip on the mechanism, or having too much weight on that type of leg.