I just made the switch last month from SPD -> SPD SL. When I was looking at new shoes those I saw some of the shoes were hybrids of sorts like yours that would accept either type of cleat which always puzzled me. My old Shimano mtn. bike shoes had rubber soles and recessed cleats. They are great to walk in. You really wouldn't know they were cycling shoes just walking in them. But having that steel SPD cleat standing proud of the sole of the shoes looked like an accident waiting to happen IMHO. SPD SL's aren't great to walk in but at least they have a little bit of grip with the soft plastic bumpers on the corners of the cleat. Get some real mtn. bike shoes with recessed cleat pockets. You don't have to spend a bunch of money, just find something that is comfortable.