There is always a big debate between those who favour the mountain-bike type of SPD - the ones with the two-hole fixing, and those who prefer the three-hole SPD SL road type of pedal.
The big advantage claimed for the two-hole type is that you can get some shoes that have a raised sole round the cleat so you can, allegedly, walk more easily in them. The big advantage claimed for the three-hole type is that they are more comfortable as they spread the load on the foot more evenly.
My preference is for the three-hole SL type, but I will confess that this is the only sort I have ever used since giving up nearly 50 years of toe-clips and straps. Mrs A chooses the two-hole type, even though she has mounted them on flat, non-recessed shoes, so she cannot walk far in them anyway.
I can walk in my SLs, but it does wear the cleats out fast. <snip>