This is funny.
Essentially no likely M3 buyer is even going to consider buying a Mustang (except maybe for his/her kid) no matter how well it does against an M3. Just not enough status or perceived engineering quality or whatever actual special stuff that the Mustang doesn't have (is there any?). The most they will do is complain that BMW should have thrown more money at making the M3 faster.
This kind of comparison is mostly about selling magazines and Ford ads. Followed closely about how it will make potential Mustang buyers feel better about the fact that most of us cannot afford an M3 . . . even if we did want one.
What is kind of funny is that an M3 used to be a relatively down to earth hot rodded 3 series . . . sort of like the faster Mustang versions. Now it is a relatively small high performance luxo barge.

Mustangs are still what M3's used to be.
But what do I know.

I drive slower cruder Mustangs and "race" a real race car. My idea of "status" has always been a popular sporty/sports car like Mustangs and Datsun Z's that the "common" man, woman, or teenager can relate to. Real automotive status begins with things like Ferrari and Lambo.

M3's just look like slightly modified 3 series that are so common around here.
Speaking of Ferrari and Lambo, did anyone see White Collar last night?