I believe black has the edge, even though this particular black one isn't as wonderfully fully ripe as the red. I tend to be drawn to the looks of the red ones more, so (fixing it in the noggin) I just need to recall, standing in front of piles of plums, that this choice is one of those matters in which attractive appearance is not a good indicator of the overall palatability/tastiness of the relationship that would follow.
Or I could just go for pluots, if they're cheap & at a good stage of readiness compared to my approximate anticipated timing for the mastication thereof.