I have both RCBS and Redding dies. I've never noticed a difference between the two of them; but I don't have them in the same calibers. Eventually, I became so impressed with the accuracy of Hornady's V-max bullets, I figured if their dies are as consistent as their bullets, that was the way to go. The last 2 die sets I've bought have been Hornady's, and I like 'em.
I have one Forster die set. I like the bullet seater die. They're more expensive. I don't know if they're worth it or not. The standard Forster seater die is cheaper than the RCBS and Redding "competition" seating dies.
Redding also has the Type S dies. If you get really obsessive about your reloading I s'pose they're worth the added cost. I haven't become that detail oriented about neck size and tension . . . yet.