eFG% is a way to assess shooting value, whereas shooting % is a way to assess the skill of shooting. When we're trying to project growth and upside I think the skill is more useful than the value metric. To say it a different way, sure it matters that Ball took a lot of threes, but he can't really take a lot more of them than he did, so unless we expect the % to go up he isn't in a good place. It would be surprising if he showed the improvement Ingram did, which to me is the point. That's especially true given his putrid shooting motion---for every Shawn Marion who makes ugly work there's plenty who do not. Thus, I don't have great optimism he'll shoot well enough to be an impact PG. Obviously, it could happen but I question why someone thinks it is likely to.
I do think defense matters, and he was better there than I expected. But my point is that if you shoot that poorly you need to be a truly elite defender, and he's not. If someone projects him to be, that's not crazy but again---as with the shooting, we're projecting a lot here.
Ingram today looks much better as an asset than he did a year ago; if Ball has a similar jump in shooting he will indeed be an even better asset than Ingram is today, given his position, defense, and other skills. But until he shows that leap, I think we have to assess what there is (strengths and gaps).