Don't know that this adds anything of worth to the conversation, but I'll chime in anyway...
Miller Coors uses corn syrup, at least in Coors Light & Miller Light, which was the basis of the ad campaign a few years back that led to Miller Coors suing AB Inbev who put out what were labeled purposely false and misleading ads announcing that Miller Coors uses corn syrup, leading the public to confuse this with high fructose corn syrup which many folks think is somehow evil or bad for you, when in fact Miller Coors uses dextrose syrup as their adjunct - same as the dried dextrose us homebrewers make use of. Budweiser uses rice as their adjunct.
I know for a fact that the effort that goes into batch-to-batch consistency at a Coors plant and a Bud/AB Inbev plant is extreme - they have staff dedicated to focusing solely on this - in house tasting panels, food scientists on staff, etc. I have known folks who worked in this capacity for both companies in Colorado.
At least a goodly portion of the barley that goes to the Colorado Coors brewery is grown in Colorado on contract specifically for them - some "high country barley" variety.
The Bud folks prize their proprietary yeast for the apple-like flavor note which has been mentioned elsewhere here.
The aging on beechwood chips done with at least the "original" Budweiser is unique to their process among the macros, I believe, for the purpose of providing greater surface area in the tank for yeast flocculation. It is not done for flavor - the long chips are steamed thoroughly ahead of time, which I was told at the brewery virtually removes any character from them. They tout this beechwood aging, perhaps purposely meaning to imply it somehow changes the character of their beer when in fact flavor shift occurs from the aging, not the beechwood.