I had a look at the keo's and the dura ace when I bought my first pair of ultegras.
I didn't buy the dura ace because they can only be attached using an allen key from the other side of the crank. There is no slot on the side for a 15mm pedal wrench.
I didn't buy the Keo's because the platform did not look as supportive, and when I asked the guy at the LBS, he said I might be better off with Shimano..