You are missing the whole point when you say "ATC may think mdf is good enough but magico does not. They cant both be right. Who is right?"
They ARE both right. Different designs and different goals. It's like saying "which is better, a Lexus or an Acura, they can't both be right." Uh, yes they can.
Everybody has different tastes and listening environment demands, and different budgets of course.
ATC are usually very true to the source, some would say a little bit "too much" truth for a home environment. BTW, the SCM25a you heard is a studio monitor; probably the least 'impressive' ATC speaker for a home environment, especially for price.