The advantage to the Polish Capper is that you can set the cap with the capper, in the same motion, after placing it on the nipple, without using a separate setter. The back of the capper (actually, the whole thing) is solid brass, and allows you to press the cap onto the nipple, not like the other cappers, where you place the cap, pull away the capper, and set the cap with a deer tine or something safer than a finger.The Polish capper was interesting...
I don't have a dog, so to speak, and I've used other cappers, and this has been my experience. YMMV.