Looks are (to my knowledge) road specific pedals. Some people like them because they have a larger cleat and they feel like they have a larger and more secure contact area. SPD (Shimano Pedaling Dynamics) can be had in both mountain and road style pedals & shoes. The advantage to me is being able to find shoes that you don't have to duck walk in. I have SPD's on all my bikes and like the compatibility and ease of finding affordable shoes and pedals that work together. My favorite shoes are a 10 year old pair of Specialized MTB shoes that are a lot like road shoes, but with some tread on the bottom. I also have a pair of Performance mountain shoes that have full tread on the bottom and are very walkable for when I'm on and off the bike. I consider them to be touring shoes.