Incidentally, by "hard and fast rules", I meant for what is in the bottle in front of you. Only bottling proof will be clear. One is unlikely to know the distilling out proof or entry proof unless some detailed research is done. Even then, the results may not be certain (for various reasons).
So if you have a bottle of high proof bourbon in front of you, it is probably more flavorful than a bottle of the same brand packaged at a lower proof. That much is clear.
But take a whiskey distilled out in the 150's, entered at 125 proof, bottled at 90 proof.
Take another whiskey distilled out at 140 proof, entered at, say,115 proof, and bottled at 86 proof. The latter may well have more taste than the other. But maybe if the former was bottled at 100 proof, it would have more taste.
I don't question Mike's statements and believe I made the same factual ones earlier. But in the final analysis, and given too that bottlings from batch to batch rarely taste identical for a variety of other reasons, one is left with just the bottling proof as a sure indicator when compared to the same brand bottled at a lower proof. But how many brands of the same whiskey are bottled at different proofs? Very Old Barton (not nationally available) is but not really since I understand the bourbons for VOB are not all the same age at the different proofs bottled (80,86, 90, 100). Old Forester is kind of an example, as between the 86 and 100, but the 100 may still be bonded, so that can distort the comparison.
Mike, any comments?