These two cuts are very different and actually come from different parts of the pig.  They look, cook and taste differently.  Pork loin is a center cut roast that is also cut into pork chops or steaks.  It is much larger in size and has a richer flavor.  It is less expensive than tenderloin and may be a better option for feeding a crowd. Tenderloin is cut from along the spine.  It is more tender and lean, with a milder taste and costs a little more per pound than pork loin.