Fillet steak is the most tender cut, and among the most expensive, but is not the most tasty because it is very lean.
When shopping for meat, the muscles that have the most marbling, the most flecks of fat mixed in with the muscle fibers, are the most flavorful.
Often the most tender, the muscles that don’t work a lot, are the most tender. For example, the tenderloin is the most tender cut, and among the most expensive, but is not the most tasty because it is very lean. Often the harder working muscles are more flavourful, but they are tougher. You can combat the chewiness by proper cooking, usually by reverse sear.
Here’s some general Knowledge about meat.
Meat is a protein sponge saturated with liquid. About 75% of meat is water.
Salt penetrates because it is a smaller molecule than water but, most importantly, because it reacts chemically with the water in the meat.
It takes salt almost 24 hours to penetrate meat 3cm deep. On top of this, most marinades have a lot of oil in them.
Meat is mostly water and as we know, oil & water don’t mix.
Marinades are for surface treatment. Only the salt penetrates deep.
End of story.