Unless one is referring to Five Ten type shoes and flat pedals with pins, the cleatless pedals work the same. The SPD-SL pedals and shoes in theory provide more support but if a shoe is made properly the sole will provide enough support with a SPD or even a clip and strap arrangement. Last year I ordered a dozen pairs of shoes to find my new pair and there was a great deal of difference in the stiffness of the soles. I want as rigid a sole as possible along with a good fit for my "normal" width feet. I found quite a difference in sizing and stiffness even within the Shimano bike shoe line.
Different companies have different ideas as to what is a normal width and normal foot pocket. People with very narrow or very fat feet need to spend more time searching for a brand that has lasts that work for them. When I find a shoe that does fit well I always buy a second pair as a future replacement.