I was thinking. This time 4 years ago you were seeing M-Frames everywhere you now see Radars. Do you really think the competitors prefer the Radar over the M-Frame or it's just that Oakley pushes them for advertising purposes? I've only seen one person wearing the M-Frame for rowing.
My guess is it's primarily because Oakley's pushing it to them, since they do want to get the latest models on athlete's faces. But I also do believe that a lot of athletes like the Radar as well, so it's their choice to wear it.
I feel it's mainly because they don't want to push the m frame out there, have many people liking it. Then discontinue it. The radar's new. So, they want people buying something current, over something they'll no longer have in the near future.(IMO)