Lamb for what it's worth is powered punched with all 8 essential amino acids and a 3-ounce serving provides 43% of an adult males protein. An added benefit for me to purchase lamb more than I do beef, is the price. The price of a tender lamb shoulder averages around $1.90 - $2.15 per shoulder where I purchase them. I have seen considerable savings switching to lamb for my red meat source.
Also there is the fat issue; lamb has less fat content than beef. So with each cut you will get a much more leaner piece of meat than compared with beef. Me personally I love fat, lets be honest fat adds flavor. But nonetheless, since I am trying to train properly and eat right "MOST" of the time having lamb on the menu has been a great choice.