a pendulum works on a balancing act of sorts. It floats on a pivot point and that can be adjusted like balancing a scale. They work only from an elevated position and only so high and up to certain angles. They are not ideal. The Keller Pendulum sold pretty well for a while but they are almost non-existent in hunting circles now days and worthless for target.

a single movable pin is in my opinion the best sight for hunters and target shooters. They are built on a sliding scale that you simply sight in left and right, then start at say 10yrds moving it up and down till it hits on the money and mark the scale. There is a pointer on the sight and you make a mark so that the mark and pointer intersect at the 10yd spot. Then you repeat it up to whatever range you want. With todays faster bows you can actually get about 80-100yds out of one....although i don't condone shooting at game past your effective range. The neat thing about these is that if you have a trail at your stand, you use a rangefinder on the shooting lane and set your sight accordingly, when a critter steps in that lane you simply shoot. If it is in an unplanned area you can guess the range and hold high or low or of course move the sight to that yardage. Most of todays bows will allow one pin accuracy to nearly 30yds with just a little or no holdover so it really isn't that big of an issue. One pin is less confusing and you always have the same sight picture no matter what yardage you are shooting. The one thing you have to do is be sure you snug the adj. knob down so that it doesn't get bumped by accident. Always give a glance at the sight setting before you shoot.