that has the higher average with runners in scoring position?

You realize that is a different metric than purely runs batted in, correct? (which as I mentioned above is a rather meaningless statistic).

Player A might have been much more successful in his RBI chances than Player B, but Player B could still have many more RBIs in that given year. In fact, this happens ALL THE TIME.

I guess it is as simple as you said it was though. I mean, you just want the guy who consistently gets the RBIs, so obviously the guy who has more RBIs is more consistent than someone with fewer RBIs. It's science.

There are probably a dozen offensive metrics that show how many runs an individual player contributes to his team that are better than RBIs.