essentially they supply different ions other than the common Calcium ions. i would not say one is better than the other as both are different things. Just like a Manesium testkit measure different parameter from a Calcium testkit, not that a Calcium or a Magnesium test kit is better.
Yes i would say both complement each other and will reach a stable stage .
in theory , using a kalk reactor will raise the pH in your system due to the hydroxide ions and using a Cr will cause a drop in pH due to the carbonic acid use to melt the media . with both used concurrently, the system will benefit to a greater extend.
Normally, a kalkreactor is used together with a top up water system.
For a calcium reactor, water can be fed to the CR from anywhere in the system . =)