Generally, road shoes are stiffer than mtb shoes, which means that any pressure is spread out more evenly along your foot. The dispersion means fewer hot spots or numbness.
However, I have MTB shoes that are identical to my road shoes except for the treads on the bottom- they're very stiff and I experience no numbness or hot spots with these puppies!
If you want to stick with the Eggbeaters, you may want to look for a stiffer MTB shoe rather than switching to road shoes. Plenty of roadies do the MTB pedal and shoe thing for the walkability of that combo.