I use the YN 560ii (manual flash) and the YN-565ex (nearly a Canon 580exii without high speed sync or a commander mode). I also have the Canon 580exii. The Yongnuos are built well, but possibly not as well as the Canon, but then they are considerably less costly. I can use use the YN-565ex and Canon 580ex nearly interchangeably except that I try not to shoot the YNs at full power for more than a few shots. My Canon cameras can't tell the difference between the 580ex and the 565ex until I try to do one of the things that that the 565ex cannot do, and then the camera menu selection for that function is not selectable. I have been quite please with the YNs and will purchase another YN (possibly the YN-568ex) again. I have been using Yongnuo gear for several years without any problems.

They are two completely different lenses. The B003 is the model number of the older model which is discontinued. The PZD (model number B008) is the newer and current version. It is a noticeably smaller and lighter lens with a filter size of 62mm. The older non PZD version is larger, heavier and has a 72mm filter size. The newer version has significantly better optics and has a PZD focus motor which is very quiet in use. What is he charging for the old version? The new PZD version can be bought brand new from B&H for $449 including the Tamron warranty.

I've attached links for both lenses on the Tamron website

B003 Discontinued Non PZD version:
http://www.tamron.com/en/photolens/di_II_all_in_one/b003.html

B008 Current PZD version
http://www.tamron.com/en/photolens/di_II_all_in_one/b008.html