Where I live, Angus Porterhouse is 10.48 lb, filet is 17.49, and ny strip is 13.49. Pretty simple math argument for me. And if you can find a place that butchers the meat in house, they usually cut it for you. I usually end up with a 6 oz filet and 12 - 14 oz strip.
All that said, most underrated is the Porterhouse, because you get 2 prime cuts for less than the price of 1.