IMHO lens tint is crucial.
Serengettis (which always reap praise in these discussions but which I have never tried) are brown tinted as are my currently favoured cebe pair. The brown tint crispens up the cloud definition no end.
Tried Raybans, Police, Randolphs, Oakleys, all the same - expensive fashion statement that makes you squirm when you break them.
I prefer contacts and shades rather than ordinary glasses and prescrition glasses - far too much of a faff in the cockpit especially in the helicopter.
Snug fit around headset is also very important.
Plastic frames are more forgiving to the misplaced derriere.
Reasonable price also very important as they will inevitably be lost, stepped on, sat on or scratched beyond recognition.
My contact lens provider sends me a free pair of el cheapo sunnies
every time I place a new order and they actually are not bad - as were the McDonalds 99p sunglasses
that were on sale a few years ago - bring em back Ronald if you're listening.
Despite the fact that I usually have about 3 pairs on the go
I can never seem to find them
. Must be scooter girl tidying up after me again!
SB