I remember back when I was a roadie I took a small spill and bent the bottom bracket on a newly built up bike. I replaced the cheaper grade BB with a higher-end one and suffered worse crashes afterwards, but never bent the BB after the upgrade. Stronger materials and heat-treatment will make for a longer lasting pedal spindle as well.
The quality of bearings also makes a huge difference. I know you're looking for platforms, but go to your LBS and feel the range of Shimano clipless pedals. The bearings on the cheaper PD-M520s are already light-years smoother than most of the competition, but wait until you feel the XT then the XTR. I almost creamed my shorts when I felt the XTR, they are SO incredibly slick.
You'll also get differences in bearing design as well as seal design. I remember buying a set of Crank Brothers Candys a while back. Man, that bearing design sucked. The bearings seized up on me on my first ride, so I took a look at the exploded diagram and was shocked to see the bearing tension was maintained using only a single nut with thread-locker on it! Those pedals went in the trash that very same day.
As for the acids, please reference these pages here:
http://www.crankbrothers.com/acid_1.php
http://www.crankbrothers.com/acid_2.php
http://www.crankbrothers.com/acid_3.php
