The point about Loretta and Miller isn't who will end up with the best career.
The point is twofold...
1) Would Miller make a significant difference today?... because that's what a lot of folks on here are insisting.
2) Will Miller make a significant difference over his years of control?
If the comparison is Loretta, the answer to both questions is no.
Loretta was worth 5.7 fWAR for the first eight years he got playing time in MLB, six of them as regular. No matter how you slice and dice it, averaging under 1 WAR per season is in no way a significant contribution, unless maybe he plays SS like Omar, or catcher like Berto.
You know who got the real value out of Loretta? The NEXT team.
So, when you look at some of the guys we have recently acquired that are playing now, think of Mark Loretta.
None of this is to say that I'm not excited about Miller. Its just that enthusiasm should always be tempered by wisdom, and expectations should be, also. My personal wisdom has been born out of watching literally hundreds of bright, young Tribe prospects arrive with the same trumpets blaring that Miller does now...and watching the VAST majority either fall flat on their faces, become a short lived shooting star, or toil for a few years in unremembered mediocrity.
Our future is bright, not because we have several can't miss prospects. We don't have even one. Our future is bright because we have a ton of very good looking prospects, and the sheer volume makes success almost certain.