Originally Posted by Iride01

Don't most work with both SPD and SPD-SL cleats or look-a-likes? The bigger thing I've found is that mountain bike shoes I've had in the past are wider externally than the typical road bike shoe. I think just because the tread on them was wider to give more balance for walking.

So if you have different types of shoes, take note if their external dimensions are bigger or not. And then if you want one pair for both, size to the biggest set of shoes.

My new SPD shoes are more typical outside dimensions to SPD-SL type shoes.

I still use the Pearl Izumi booties I bought many years ago. However I don't usually ride in 20°F temps. I know, I'm a wuss for not being more determined to ride.