As far as the FL dies I prefer the Hornady because of the elliptical expander ball. Now when you add in the seating die it is Hornady hands down, love the sliding sleeve seater. I usually buy a Hornady seater to go with whatever FL die I have.
As far as RCBS dies go I don't see them as anything special, I have Lyman,Pacific, Herters, C&H(one of my favorite incredible die list and great price) and a couple without names that are as good as RCBS, heck even Lee makes a good reloading die if you can live with their lock ring. RCBS is much like Leupold nothing really outstanding other than their Customer services and that is top notch.
If you are dealing with something antique, unique wildcat or just off the wall C&H might have the die in stock or can build you a die set considerably less than a custom die from the big four. I need a die set for a 6.5x58 Rimmed Sauer(it looks like a giant 22 Hornet and has been out of production since the 1930's) C&H had a set on the shelf plus a bullet sizing die to take .264 bullets to .260 to match the bore diameter of this particular rifle.