Check to be sure that your pedal isn't touching the lugs on the bottom of your shoes. If the pedal is touching a lug, that is where you need to cut away some material. A Dremel tool works well.

If you have the same pedals on both bikes and they don't perform the same way, you've got tension adjustment or lube or cleaning issues. The pedals on your mtbike will probably take a lot more maintenance.

Crank Bros pedals were harder? Did you have the cleat turned to the easier position?