They are different cuts of meat. Pork loin is much bigger than pork tenderloins. Pork tenderloins are usually around 1 lb, while boneless pork loins are usually 2-4 lbs in weight. The bigger size of the pork loin means it will take longer to cook. A pork loin also often comes with a layer of fat on top, while a tenderloin is much more lean cut of meat.