I choose darwins to make a buy&hold portofolio, so I like that they are uncorrelated. This may sound obvious, but for instance to make a portfolio right now I'd need that the darwins inside it would work together without losing too much from 01/08/2018 until december that year or so. There are darwins that seemed very good until those days, and then all of them went down at the same time. Not good for a portfolio. I wouldn't even need profit, but just not losing too much in those moments.
I like high Mc because that means that the trader is able to ride both sides of the market. Said that, I also like some darwins like YZZ, BSL or EZN although they have not-very-high Mc because they seem (medium-term) uncorrelated with other darwins. So for the portfolio are good.
Also Rs > 6.5 or so (it would depend, for instance in PME it is lower but that's probably because he just trade from time to time).
But honestly, I'm starting to think (thanks to @CavaliereVerde), that one of the most important things is a long (>2Y) native trackrecord...