This all comes down to personal preference. St Louis-style ribs tend to be meatier than the baby back versions. The belly of the pig is cut out, and then the ribs are cut from the belly area. They are then trimmed down so that the cartilage and breastbone are removed. They are relatively flat which makes them easier to brown during the cooking process. This marbling of fat also provides a richer and more intense flavor profile.
Baby back ribs come from the meeting point of the spine and ribs of the pig. They are cut out after the loin has been separated from the carcass. They are referred to as baby back ribs as they are shorter than spare ribs. They tend to range in length from around 3 to 6 inches.