You can't beat the cost at Dr. Foster and Smith. $5X plus free shipping. At that, why not go with RC unless you need is now.
What I am doing now is dosing to the parameters that I run in the system, this way I rely less on dosing into the tank although it is is still needed regardless if you have an established tank.
One thing I know for sure is that RC has higher mag and I believe higher alkalinity. For some higher alkalinity is an issue because of the volume the change in water. Me, not so much as I have an automatic water changing system so the amount of "extra" alkalinity helps me keep my alkalinity slightly higher or on point as the SPS take it in.