Maybe I was using the wrong MTB pedals (I used on my road bike/am using on my MTB Shimano SPD style 500 something) but they never felt as secure as my road pedals. There's some play between the pedal and cleat that allows some rocking. I also like them very tight and could not get the SPDs as tight as my Keos. I've pulled my foot out of the SPDs while standing and sprinting, but that's never happened to my Keos. So that's all I meant by "more secure".

I guess I misspoke with the larger platform. I just meant they are better at having a larger platform, because they mostly do (not exactly the best wording in retrospect). The benifit of the larger platform I guess is debatable but there's a good arguement that larger is better (and has been my experience). More surface area spreads the force on the bottom of the shoe out over a larger area - thus there is less force on any given spot. If the sole of your shoe is flexy this can cause a hot spot where all the pressure is located. A very stiff carbon sole also helps distribute that pressure and could overcome some of the problems with a small platform. At least, that's been mine and everyone who I can think of who I know who's ridden road and MTB pedals' experience. YMMV though