Probably not what you had in mind, but works great for me: power grips straps and then whatever shoes you want to wear.
My guess is that I may lose some marginal power % compared to clipless, so for rides where getting my absolute 100% performance is critical, I do clipless. My tri bike has clipless pedals.
For commuting/touring the difference is minimal to nonexistent and I much prefer the footwear versatility based on weather and whatever else I plan to do when I get there.