On corrosion resistance, 9Cr18Mov is a slam dunk over D2. On edge retention, heat treatment can make a world of difference.
In the video I posted earlier, Civivi's 9Cr18Mov didn't just smoke Real Steel's 9Cr18Mov on edge retention. It also smoked their own D2. The thing with D2 is that its reputation for edge retention was built by more expensive knives with better heat treatments. Chinese D2 is another animal. It's mass-produced on a budget scale. There also seems to be some variance in composition. Under the particular test conditions used by Outpost 76, Chinese D2 is all over the place on performance. Some perform quite well but the average is pretty disappointing.
The way I see it, D2 is a trade-off that supposedly gives you better edge retention for less corrosion resistance. If it has trouble competing with genuinely stainless budget steels like 12C27, 14C28N, or even the less stellar 9Cr18Mov from Real Steel; that doesn't seem like a good deal.
BTW, AR-RPM9 doesn't seem to offer much over 9Cr18Mov in edge retention (for now, I'm hoping). Under the same test conditions, results were on par with Real Steel's 9Cr18Mov. In other words, Civivi's regular 9Cr18ov was a lot better. Given the powdered metallurgy and tweaks to composition, we expected better things from AR-RPM9. It could just be that they haven't figured out a good heat treatment for it (yet, I'm hoping).