mnichols wrote:That's an interesting point, but in a touring shoe where the sole may not be that rigid does the broader pedal help?
Yes, of course it can, depending on how rigid the sole might be. However, try for yourself - good touring/MTB shoes are designed to flex upwards a bit (for walking) but not downwards (for pedalling). By contrast, racing shoes just don't flex at all.
Some of the alternative designs, including Speedplays and Eggbeaters, are used for mountain biking and aren't obviously about support at all, but more about limiting the effects of mud on the engaging and releasing processes. By contrast, most race and sporting riders use variants on the Look design (including Shimano and other rough equivalents), which probably provide more support than any other, albeit with cleats sticking out underneath because they aren't intended for walking at all.