Curl,
RCBS make great dies for sure and I've always had a good run with them in the common chamberings.
I wish I could say the same for my doubles though.
I have two sets of RCBS dies for doubles, one in .470 NE and the other in 400-350 NE.
The 470 set has the shoulder too far forward by a mile.
I believe they have corrected that on current sets though.
The 400-350 set is oversize in the neck sizing section and will not reduce the neck diameter enough.
You can ditch the expander or leave it in cause it doesn't make any difference as it doesn't ever come in contact with the case.

Many don't like CH dies but I have owned a set in 360 No2 and another set in 300 Savage which were both fine.

Does all this mean that I'm saying CH is good and RCBS is no good?
Definately not, but it does demonstrate that you could end up with good or bad in either or any brand.
I think RCBS is still the best option though.

I doubt that RCBS used to make two different FL dies in 450-400 3 1/4" for the two different bullet sizes of .408 and .411 though. (talking non-custom dies)
This may be different now but it is possible that they just did a .408" full length die and either did two different expander diameters or maybe just one "average" expander at about .407" or .408" actual diameter.
That would have worked for either the .408 or the .411 but would have left the .408 with minimum neck tension as 400 NE experienced.