For both being rated similarly, yes, it does perform better as far as skimmate production and even just darker skimmate. I mentioned it in another thread but I'm still a huge fan of the Skimz build quality and performance, I just think they have their ratings a tad higher than they should be.
For CaRX, I've run both dosers and CaRX, though dosers for a much more limited time, and I will say that a perfectly calibrated CaRX in my opinion is way less work. With my old Korallin, I topped off media, recalibrated my pH probe, and swapped my CO2 cylinder every 6 months. That's 2x/year of maintenance for rock solid alk, Ca, and Mg levels... Not to mention probably many more trace elements as you are melting down old coral skeletons instead of just dosing straight calcium and alk like in a 2-part dosing systen.