If you plan to ride anything other than smooth gravel roads, go with MTB pedals. Most of the "gravel" events, in my area, involve some amount of singletrack to connect gravel road sections. It's not fun to try to clip into a one sided pedal on rocky/rooty singletrack. If you have to do any walking, you will quickly destroy a set of road cleats and road cleats do not offer any traction for off road hiking.