Both cuts are from an area at the back of the cow between the short loin and the round, but the top sirloin is much more tender (it sits right next to the tenderloin). Because it's the prime cut ...
Sirloin cuts make sirloin steaks or tri-tip roasts ... Filet Mignon. The short loin cut of beef has the most popular cuts around, including porterhouse, T-bone, New York strip, and filet mignon.