I selected the Zeros for the adjustability and being the most their current design.

I had been using SPDs and XT MTB pedals on the road bike and my joints were happy - didn't want to get the float too far from what was working.

Light Actions have the full 15 degrees of the design without the ability to reduce it. The X Series is the prior generation, and I try to avoid that with things I expect to use for several years - cuts down on the urge to "upgrade". I moved away from the SPDs due to hot spots on longer rides (for me that's been 25+ miles).

That said, it's taken a few rides and time at the bench to get the cleat position and float adjusted. Not quite there yet, but I won't go back to the SPDs. If I can't get the Zeros to a comfortable place, I'll try SPD-SLs.