Tint in vermillion or amber is a jolly useful thing for low contrast moderate light conditions like flat light in snow. It ups the contrast perception from bugger all to a little more, nut that can be very useful. Otherwise tints just make stuff a weird colour...
Super-dark handy for bright sun on snow, or general sun if you have sensitive eyes. My glacier glasses are a deep brown but it's just cutting out a lot of light that I like them for, the colour's not really an issue for me
Polarised can be nice if you're paddling or sailing, or otherwise in high glare 9say, sun glare off wet rock).
The only reason I use an expensive set of sunglasses rather than a pair of "safety" sunglasses for walking (you can get a perfectly respectable pair of Bolles with a fixed lens and grey tint for about £6 from the RS catalogue, or various cheap cycling sets with changing lenses for around a tenner) is it means I can put a prescription insert in, not possible with cheapies, but only relevant if you have corrected vision.
For most purposes a grey tint is fine (you're just cutting light out, but not changing the colour). There's little to be gained by getting anything fancy, especially as "names" like Bolle really do sell similar things as safety glasses for a tenth of the price.
Pete.