Ride SPD on road bike, and regular BMX style pedals on commuter bike. The only time i'd like SPDs on the commuter is when it rains. No matter how studded regular pedals are, feet will slip a bit when jumping over potholes etc. So that's the biggest advantage of SPDs IMO - you're with your bike, locked, securely. However, SPDs are a bit too inconvenient for commuting, most of the time. For me at least.