This is a long lasting debate in the hardscape industry, our answer? You can do both right and you can do both wrong. This is where a good reputable contractor comes in.
Depending on the project one base material might be the proper way to go over the other. The way in which the RCA is compacted, the depth of the RCA and the type of traffic will depend on how well it lasts. Concrete too can be called for on certain projects and the depth at which it is poured, its pitch, drainage, and finish process can all effect how long it will hold up over the years to come.
Other things to keep in mind would be we live in Long Island and have climate that truly faces all of the seasons. With a freeze thaw cycle that can be extreme one base might fit your project compared to the other; again this is where a qualified contractor comes into play.
Looking to do a D.I.Y.? Stop in to our Ridge NY office for some helpful advice, at the end of the day it falls back to the beginning statement, you can do both right and you can do both wrong, but our staff or recommended contractors can help you decide the right method.