Anyone saying clipless pedals with proper bike boots are not more efficient then flats with shoes that are cool for walking around all day long, have obviously A. never pedal or B. doesn't know a thing about efficiency. But either way, I would suggest you to use some proper shoes with carbon soles, clipped in and you will see that there's simply no way that any flat pedals with those cool looking soft shoes would come anywhere near efficiency of carbon sole clipped into pedals.
Just as in skiing, also in cycling racers actually use stuff because it's fast and efficient and much less because it looks cool and current fashion says it's best thing after white bread. There were few such things before in mtb, from Cannondale riders using baggies, to DH riders complaining that lycra doesn't look cool and UCI should make rule preventing lycra in DH. Which they did, but several years later, with rule still in place, all DH guys are running super tight, non-lycra suits even if they don't look so cool, and Cannondale dropped their baggies, after it was clear that looking cool doesn't make you fast (even with mtb, wind resistance is pretty much main factor).
But no matter what, I would dare to bet, there was not a single racer on XC world cup, that would show on start in Five Ten and flats. Could be because they are traditionalist who have no idea what's good, but more possible is, because they know flats are nowhere near as fast and efficient as clipless.
Another thing for this so important different stance on bike, distributing weight once like this other time like that. Really? Seriously? I admit I'm more xc guy, but I have no issues riding down steep stuff full of rocks and roots with my xc bike, seat 10cm above handlebar and clipped in. Sure, I'm slower then guys on DH bikes, but still faster then most of friends with similar way of thinking as big part of posters here, who actually walk down in their comfortable shoes, as it's too hard, to steep and too rocky to ride down. On other side, I would dare to bet, most of all these people would have serious issues getting down some sections of xc WC race, where guys and girls in lycra clipped in speed down, sometimes even on hardtails, most of them without droper posts, and all of them on bikes with geometry so different to what most of you ride, that you would consider those bikes unridable on anything but flat gravel
