Originally Posted by Walpurgisnacht

I've never seen a Click'r pedal offline, and it's pretty hard to tell from internet images of the Click'r pedals. It looks to me like the pedal platform is pretty flat, and level or very close to being level with the center of the pedal. Compare this with the M324, where the platform side has "teeth" that are raised while the center portion slopes downward a bit. Mountain-style cycling shoes have the cleat recessed pretty well, but the M324 provides enough of a gap that even if your shoe exposes more of the cleat, or if your foot strikes the pedal at an angle where the cleat would strike first, it's unlikely that the cleat would hit the pedal. That saves wear-and-tear on your cleat, and might be safer (no risk of your foot skidding even slightly across the pedal).

Long story short, the Click'r pedals might work for you, but a lot will depend on your shoes. The M324s (or a variant made by another company that looks very similar, "campus pedals" is the product name I believe) are your safest bet when paired with mountain-style shoes that look to have good traction on the bottom.

As to power/efficiency, I saw an interesting chart examining muscle recruitment during the various parts of the pedaling cycle. One chart was produced by someone surmising which muscles are used, and how clipless could improve upon that; another chart looked at measurements made using the electrical activity of the muscles to find out when they were actually being used. Long story short, clipless didn't provide any benefit. It's true that you can pedal on the upstrokes while being clipped in - a sensation that I found to be somewhat empowering when racing up an incline - but it's questionable how beneficial that really is.