You seriously can't taste the difference between pasture-raised beef and the grade D swill that junk food pushers like In-n-out peddle?
As you might have inferred by now, good burgers are typically made from cuts like brisket and chuck that are tough, inexpensive, and high in flavor. Using high-end steaks for burgers is simply a waste, doubly so for well-marbled ones.
The fat percentage would not be difficult. Any good butcher would probably be happy to help you set such a comparison up. That is, if they don't warn you that it's a waste to use that T-bone on a burger first.