Maybe ERA is one of the things they factor into fWAR. I have no idea. As far as I know fWAR is just something that a guy with a website invented. As for which of your groups is best, it's all a matter of opinion. As a rule, I would say that the guys with the best ERAs are usually the best pitchers. But there is something to be said for the guys who consistently win games. And there are pitchers who seem to have good stuff and good metrics, etc, but never really become big winners. In the end, winning is what matters most.