David, I have not processed Cibachromes in many years, and I am no expert, but I think the best way to compare Ciba's to RA-4 is to look at the differences.
Very subtle adjustments of time and color will result in huge changes in RA-4 prints, while obtaining subtle changes in Cibachromes require huge adjustments of time and color. One requires a very soft touch, the other, a sledge hammer.
Color and density adjustments are opposite. If an RA-4 print is too yellow, yellow is added to the filter pack to remove it from the print. If a Cibachrome print is too yellow, yellow is removed from the filter pack or cyan & magenta added to correct the print. Printing Cibachromes is the only time the cyan dial on my enlarger ever leaves "zero."
RA-4 chemistry is pretty mild stuff, diluted that is. Cibachrome chemistry is down right nasty! The first time I saw the "Yellow cloud" rising from my processing tube, I was sure something was going to melt. As it turns out, it was the trap below my kitchen sink. I replaced a few traps before I learned to dump the spent chemistry in a bucket of water before dumping it down the drain.
Contrast can be excessive with Cibachromes, often requiring a mask, or some very artful burning & dodging. I have often found RA-4 prints soft and muted by comparison.
Still, there is no substitute for a Cibachrome. Sometimes I wonder if they have a secret battery compartment.