This will no doubt bring the engineers out of the woodwork, but I gotta posit: do listeners REALLY notice the subtle differences in the way each station sounds? I'm especially thinking of loudness here. At this point, stations are all generally uniformly loud. Does it REALLY affect one's perception of a station if one is crushingly loud and the other is more reasonable?
I wouldn't think there's a whole lot of noise or interference to overcome in these markets, what with all our big signals on bigger sticks, so it's not like the loudness is needed to cover up static. So what purpose does it really serve? I remember when Birmingham's oldies station (106.9 WODL) flipped to classic hits as "The Eagle", someone came in and completely revamped the processing. It got much quieter, but the sound quality overall was stellar. Even being the radio nerd I am, I thought to myself, "I didn't know FM could sound this good!" They traded loudness for full spectrum reproduction and it was an eye-opener. Of course, that only lasted about six months, IIRC, before they changed it back to be loud as everyone else. But those few months, that was about the only station I listened to, and going back to higher levels spoiled me off radio for a while.
The reason I bring this up is because at the time I was working in an open industrial site where everyone had their own radio, and no one complained about them being too quiet (or Rock 99 suddenly seeming louder by comparison). In fact, in six years the only person who ever commented on the way any particular station sounded was a rap fan who commented that 95-7 Jamz "really thumps in my car compared to everyone else" — Jamz and sister station Kiss FM both trade loudness for robust lows and highs that really stands out for sounding so clean. (I think BLX also has traded some loudness for low end oomph, but I only have listened in HD which may be totally different processing.)
Granted, this is a very minor sample, but if anything it says to me that some folks will notice a less aggressively processed station, but won't notice subtle differences between two very loud competitors. So why bother?