Do you shoot the large bruiser that offers a good shot or do you shoot the old buck that is declining in size and in physical condition? The answer I have used on the past and want to know if I am right or wrong is, I only shoot bucks that I would mount.
There is no right or wrong answer to this question. But I would say that in the wild, "the old buck that is declining in size and in physical condition" is a rare, rare animal.
Of all the elements of QDM, what buck to harvest is the most over-studied issue. Everyone wants to discuss that, but too few want to look closely at doe harvest, habitat improvement, or herd monitoring. I would suggest that you simply set some kind of standard that encourages doe harvest and makes you think twice before taking a buck. For me, that means trying to hold out for bucks of 3.5 or older.