I've commuted in SPD SL for the last 5+ years because I wanted the same pedal system on all of my bikes and most of my miles used to be on road bikes.
I've just switched to SPDs and the only difference I can tell is that they offer a smaller contact point with my shoes and feet. That could just be the fact that I'm riding in £30 shoes instead of £250 shoes now though.
I've commuted in SPD SL for the last 5+ years because I wanted the same pedal system on all of my bikes and most of my miles used to be on road bikes.
I've just switched to SPDs and the only difference I can tell is that they offer a smaller contact point with my shoes and feet. That could just be the fact that I'm riding in £30 shoes instead of £250 shoes now though.