I also agree. But, the biggest benefit of the SPD-SL/LOOK pedal and cleat, is that they provide a big platform for power transfer.

All clipless pedals are not created equal. Yes, the essentially do the same thing, but in much different ways. MTB pedals are designed to shed mud first because if they can't deal with mud, no MTB/CX rider will ever use them. The second factor is making them easy to get in and out of because MTB/CX riding involves LOTS of high-speed hopping on and off the bike. This is why they are all double-sided. Float is not a priority in MTB pedals. Yes, they have float, but it's not a priority when engineering them. There are very few cleat placement (fore/aft, left/right & angle) options.

Road pedals, on the other hand, have different priorities. Power transfer is the first. This is why the platforms are wider. Cleat placement is the second. You can adjust the cleat fore/aft, left/right, and set the angle. Float is the third. These are important because they are made for people riding repetitively for several hours at a time.

If you are a bike messenger getting on and off the bike several times an hour, go with MTB style. If you are a commuter, city rider, student where you get on when you start your ride and get off when you get to your destination and only get off a few times an hour (stop lights and what not) then go with road.

I've owned both styles and happened to own TIME ATAC and Shimano Ultegra SPD-SL on two different bikes at the same time. I rode the bike with Ultegra pedals for a few weeks then one day decided to go for a 1hr ride on the bike with the TIME pedals and man...those pedals felt primative compared to the road style pedals. It was night and day. Like Mono to Stereo, B&W TV to Color.

I don't get benefit from you getting one kind of pedal over the next. I'm just passing on my experiences.