Really hard to say. Many people like the wave cults too. I think the EVOs are more hard core wave riding oriented. Many people like them for hih wind freestyle too, but they do not have as much compromise towards give you the classical straightline feel as the RRD. In other words, the RD offers a "sharper" ride.
I think I can confidently say an EVO will have a wider range once on the wave. It performs both in small and slow waves, but also in bigger faster waves due to its kind of "calm" ride. Taking into account the RRD is a bit smaller, I think that the EVO might have a wave performance edge in slow wave and with big sails.
Despite some difference in width, I don't think the EVO 70 would be so good as a complement to the Cult 68. There will be an almost 100% overlap when it comes to sail sizes. The Cult is narrower and slightly smaller, but has a faster rocker. The EVO is wider but has a slower rocker. At your weight, think you will be able to put just as big a sail on both of them. In high wind, the calmness of the EVO will pretty much cancel the width difference and be about as easy to control as the Cult (this depends a bit on your sailing style too though).
The feel is different though, so if the price is good and you want to widen your views on what kind of curves one can draw on a wave face, the EVO might still be a nice addition.