I found that on longer, harder rides, my feet would sometimes go numb with SPDs. Road shoes and cleats seem to help that.

For my commute they don't have any particular advantage except that I sometimes like to commute on my road bike which sometimes has the road pedals on it. The SPD-SL road cleats have little rubber nubs on them so they aren't awful to walk on but they're just plastic and walking long distances on them will wear them out quicker. There are cleat covers which help.

Lake used to make a road shoe designed for commuting. I snagged a pair on Ebay. They work OK but it's a bit harder to clip in with them. Anyway, I did try for awhile to make road shoes and cleats work for commuting but unless you have a specific reason for wanting to use them, I'd stick with SPDs.