Originally Posted by Smokehouse

Personally...I actually found SPD-SL much easier to walk in the SPD. The two rubber feet on the rear of the cleat (SL) offer a "tripod" with the single heel point. Once you get used to having your feet a bit turned up...I found walking to be extremely easy (I mean it). On the other hand, SPD is extremely small and when I put that cleat on a pair of road shoes, I actually found myself rolling my ankles often if I didn't pay close attention. Unlike the tripod of the SL, all you have is your heel...and a tiny metal cleat dead center of your foot...rolling an ankle is easy. In a pair of MTB shoes, the SPD isn't as bad...but MTN shoes are more "flexy", far less vented and as others have noted...heavy. Add to that the fact that SPD only pedals are limited and heavy...once you go to SPD-SL, you're options are much better.