Shimano PD-6800 vs PD-9000 pedals Other than a 12g saving in weight and the Dura Ace label, are there any further potential reasons to prefer Shimano PD-9000 pedals over PD-6800?

Edit: This question is specifically about pedals rather than general Dura Ace vs Ultegra comparison.
In addition to the points noted in other answers, there is a significant technical difference: bearings.  Traditionally, Dura-Ace equipment with bearings has had much better quality bearings/races/cups/seals/etc. That appears to be true here as well. Look at the parts breakdown documents from shimano and you'll see a significant difference in the axle/bearing setup:


PD-6800 - 12 ball bearings inboard, 12 outboard with bushing between
PD-9000 - 17 ball bearings inboard, 9 outboard with needle bearing between


The bearings in the 9000 will live much longer and deal with intense loads better than the 6800. That said, the 6800 is a fine pedal.