Too many options.
SPD systems best for being able to walk, not so great for clipping in and out and cleat surface area, cheap
SPD-SL ok for walking, good for clipping and good surface area, not so cheap
Speedplay frogs, can be ok for walking and very convenient, not cheap

Say platforms give me 50% efficiency, I'm looking for the cheapest solution that gets me to 80% efficiency and suits my needs above.