My thoughts here:
- There's no evidence that stiff shoes are more "efficient". It is true that stiff soles are more comfortable in hour three.
- Modern massive pinned MTB pedals offer amazing grip that's close to clipless and can be used with any shoes. I'm a big believer in them.
- Clipity-clop road shoes are great for racing and long road race training rides. If you're not racing, forget road shoes.
- Mountain bike shoes are far more practical for the vast majority of people than road shoes.
- SPD pedals are terrific. SPD-SLs are terrific if you're racing.
- Crocs make great riding shoes with pinned pedals.