This ain't bad:
Marbling makes a steak more juicy. Filets are tender because of where they come from on the cow.
In general, the least-worked muscles are the most tender and the least flavorful, while the reverse is true of the most-worked muscles. Filets also tend to be cooked medium rare, or rarer. The longer you cook a steak, the tougher and less flavorful it gets.
JR