I am partial to the single bearing arm. It allows, as does none other, for an effectively friction-less bearing. When I moved to a 3D arm wand, I discovered that I HAD to change the lower bearing as the old one (with the cup) did not work with the newer arm. I believe the newer one is made of a more durable material than before.
All that said, and much as I had avoided the dual pivot* because it seemed to be at odds with the idea of the unipivot, I tried it and I like it. Though it's a contraption, it is one that works and, properly set up--leaving the great bulk of the weight on the original pivot--it is responsive to virtually every problem raised about the single bearing arm. As a bonus, it makes setting azimuth crazy easy.
*my remaining question about it was resolved by the availability of the ruby ball point.
All that said, and much as I had avoided the dual pivot* because it seemed to be at odds with the idea of the unipivot, I tried it and I like it. Though it's a contraption, it is one that works and, properly set up--leaving the great bulk of the weight on the original pivot--it is responsive to virtually every problem raised about the single bearing arm. As a bonus, it makes setting azimuth crazy easy.
*my remaining question about it was resolved by the availability of the ruby ball point.