Originally Posted by
Caliper
If you just want to operate a gravel bike on the road, sure. Then there is no need to change wheels even. But, you are definitely giving up connection plus adding weight to your feet and remember that his test was about actually being competitive on the road. If I had to pick just one pedal and shoe it would be three bolt road cleats and shoes since I rarely unclip on gravel rides anyways.
I've been using the Shimano PD-A600 road pedals on my road bike for years, and I really don't think I'm giving anything up at all. Nothing but gains. There are even stiffer road shoes available for SPD cleats that allow you to walk far better than SPD-SL or Look style cleats do. Power transfer comes mostly from the shoes anyway.
I come from a mountain biking background in the 90's, so I had great familiarity with the old SPD standard. And I have some knee trouble at times, so I appreciate the extra float in the SPD system. I use the single-direction release and have never had an issue getting unclipped.
I would also consider Speedplay, but it's just difficult to switch over all of my shoes and bikes once you're invested in another system. But I do believe road shoes cold be fine in gravel as well, if that's what you prefer. Mud has been an issue for some, but not every gravel rider routinely rides through peanut butter.