When picking out any kind of eye protection, comfort is at the top of the list, because if you don't like your equipment, you are less likely to use it, and that's not good.
When considering goggles for skiing or snowboarding, be honest with yourself about what is most important - performance or appearance. The mountain is a very social place, and it's fair to say that looking good can be a part of feeling good. Be careful that the goggles that match your outfit actually work, however, or you'll spend too much time recovering from wipeouts, and it's hard for anyone to look good doing that.
Goggles perform three main functions; eliminate wind, improve vision, and protect the eyes from physical harm. The quality and performance of most equipment is indicated by the price, so that is a good place to start when considering performance, but what are you paying for?
The biggest concern about goggle performance is fogging. When you put on goggles, you create an enclosed space around your eyes. Moisture is always being given off by our warm skin, and when that warm, moist air hits the cooler lens surface, the water condenses and you get fogged up.
Almost all snow goggles on the market today have a dual lens construction where an outer tinted lens is combined with a clear inner layer with a seal creating a dead air space which allows the inner surface to be warmer and thus reduce fogging. Fog can be further reduced by treating the inner lens surface so water droplets are less likely to form, and goggle manufacturers treat the lenses at the factory, but the coating can wear off and must be renewed.
The best fog-avoidance method is a well-ventilated goggle that reduces or eliminates the buildup of moisture. This is where the features and design of a goggle become important.
When you pick up the goggles, look the the top and bottom of the frame and note the surface area of the open-cell foam vents. The lens should also have vents across the top. The larger these vent areas, the faster fresh air will circulate. When you are trying them on, walk around a bit- you should feel air moving through. They should also have a good, comfortable seal to your face. Better goggles will have multi-layer foam with a softer finish against the skin.
As you check out the frame construction, you'll notice differences in the lenses. The lens is far and away the most important and costly part of any goggle. The color, materials, and construction separate goggles you forget you're wearing from the pair you curse and throw away.
Better goggles will have a wider range of lens colors, tints, and features including spherical lens designs for improved clarity and field of view.
Lens color and tint
Consider the surface you are skiing or snowboarding - snowflakes are transparent but actually very shiny, so when they pile up, you get lots of reflected white light, creating uncomfortable glare and difficulty discerning changes in terrain.
Lens tint and color will reduce glare and improve contrast. The tint will be described by a rating system based on how much light is allowed through the lens, or the Visible Light Transmission level. A VLT of 30 allows 30% of available light through, which would be suitable for medium to bright light. Move up or down the scale for anticipated conditions.
The color will affect the accuracy of colors around you, so consider what you will be looking at. Yellow lenses distort most colors, especially blue, but are excellent for contrast, and tend to be high VLT so are best suited for night or heavy overcast conditions. Grey has the least effect on color perception and is available in a wide range of tints. Rose, gold or other red or orange-based lenses will increase the intensity of red and greatly improve contrast at mid-VLT tints, so many goggle companies classify a lens in this tint range to be 'general-purpose.'
Some lenses will have a reflective or mirror coating to further reduce glare. A mid-VLT lens mirrored lens can be more effective than a lower-VLT non mirrored lens, but will be more expensive.
Polarization is most effective when the light reaching your eye is of a consistent wavelength, like reflections off water, glass, or chrome. Because snow reflects at many angles, polarization is less valuable in a snow goggle. Because of the flexible nature of goggle lenses, good polarized lenses are also costly to manufacture
Good goggle habits
The most expensive mega-featured goggles will still fog if you don't treat them right. Some basics:
Beware of rubbing anything on the inside of the lens- this can remove the factory anti-fog coating and possible scratch the surface. To remove moisture use hot air (hand dryer in the restroom) or blot carefully.
Warm moist air is your enemy, and the top of your head is a prime source, so do not put your goggles anywhere on your head except your face. Top of the helmet is fine for a short period, but don't leave them there, stretching out the strap. This goes double for the goggle pocket inside you jacket - use that only when you're not wearing the jacket.
A storage bag will help keep your goggles clean and scratch-free. If your goggles don't come with one, ask the shop if they sell them separately.