Porterhouse steak is a large cut, usually taken from the loin of the animal. It is one of the most popular restaurant choices. Rib Eye steak is cut from the ribs and tends to contain fat. It is one of the juiciest cuts and the fat lends it lots of flavor. It is one of the most expensive types of steak.
Steak is usually cut against the grain of the muscle and usually from the hindquarter and forequarter in the case beef. The tenderness and quality of a steak are determined by how much work the muscles did while the animal was alive. Steaks cut from heavily used muscles, such as from the shoulder area, are less tender and less expensive than cuts from the loin. Steaks are usually chosen for their flavor or tenderness. The fattier cuts tend to be more flavorful.
Porterhouse steak is cut from the rump end of the short loin. It contains a t-shaped bone and is part tenderloin and part fillet steak. It is more tender than "T-Bone." The bone and the mixed muscles pose a challenge when cooking, as it requires longer cooking times than most other steaks to ensure a proper degree of doneness, especially in the areas closest to the bone. It is a very large steak, with good flavor. The mixed nature of the meat results in different levels of tenderness throughout the entire steak.
Rib Eye steak, also known as Scotch Fillet in New Zealand and Australia, is cut from the eye of fore wing rib area of the animal. It is a large, round steak which tends to be marbled with fat. Rib Eye steaks are either sold with the bone still attached, or boneless. They are very flavorful and popularly used for barbeques, as they are best eaten rare or medium rare. They tend to contain more fat than other types of steak.
There are some generally accepted standards for cooking steaks, known as "doneness." The levels of doneness, in increasing order, are bleu, rare, medium rare, medium, medium well and well done. Rib Eye steak lends itself well to the lower levels of doneness, while Porterhouse steak is best enjoyed at the higher levels.