is there any difference in the FL dies? I would assume they all be the same as far as features and concentricity, I mean all they have to do is size to SAAMI specs am I right or mising something?

six of one....half a dozen of another

The Redding Type S bushing die works great for my 708 and everything else that I load. I use the Forster Comp Seater.

which FL dies produce the best concentricity?

I have 3 different FL dies (plus a Lee Loader) for the 7-08 and they all make good ammo. Soooo, pick your poison.

most of my dies including the 7-08 are RCBS.. not saying they are the best, thats just what i have. and customer service is so easy to deal with. i do have some hornady and lee..

Glad you asked about concentricity. When you order your bushing sizes correctly you will find that you do not need the expander ball on the Redding Types S bushing die. In standard dies the expander ball can cause concentricity problems when pulling the case out of the die. Another benefit of the bushing die is that it does not over squeeze the neck and you get more life from the brass.