I don't have enough experience to be of much help. All I know is that I like them, and they seem easier to use than the two-sided SPDs I have on my Trek. I was nervous in a part of town I live near (lots of quick intersections, busy traffic and pedestrians, and no bike lane) and need to ride through to get pretty much anywhere else I want to go. I wasn't clipping in with the SPDs out of fear of not being able to get out or back in fast enough. I don't have that fear at all with the Speedplays, even though I've only used them for two days. They've given me confidence (hopefully, not false confidence....eeek).
2013 Kirk Frameworks JK Special/Selle Anatomica
2012 Gunnar Sport/Brooks B17
2001 Calfee Tetra Pro/Selle Anatomica
1984 Raleigh Sport/Brooks B66