From an architectural point of view, St. Pancras (since it was done up) is hard to beat but on a personal level, Dawlish as I remember it from childhood holidays in the late 70s and early 80s wins. Back then, it seemed like an almost constant procession of trains with a great variety of loco types; classes 25, 31, 33, 37, 45, 46, 47 and 50. Happy days.