cipio
Pre-takeoff checklist
You want good optical quality sunglasses.
Great point. One I completely failed to even mention. Testing optical quality is another beast altogether. I believe inexpensive glasses can have great optical quality/clarity, but it's a crap shoot. I suppose that's the one thing you are more guaranteed of with the expensive ones. For example, I have no idea who makes the lenses for these glasses, but like just about everything else, there's a factory that makes lenses for about a billion different brand names! ;-)
I did some quick tests with a laser, and also a clarity chart, and I can't see any notable difference from my Oakleys...but I am sure there is more to it than I am seeing (pun slightly intended).