Bolle Tracker II
The most important thing is that you get something that fits your head snugly, offers sufficient protection and that you're comfortable. Beyond that it's simply about choosing lens type (clear, yellow, or smoked).
Yellow lenses amplify ambient light, making it easier to see, however as it tints everything, colours can be harder to make out. Clear lenses offer a simple shield/barrier, and translate the image exactly as you'd normally see it. Smoked lenses offer protection from the sun, however as they limit the amount of light getting through, they are more difficult to see in low-light conditions
The Bollé Tracker II glasses are pretty much the industry standard in eye protection - a combination of goggles and glasses, with a full seal to protect against particulates getting at your eyes. Included with the glasses is a handy microfibre pouch, perfect for cleaning and transporting your eye protection. The glasses come with both ear pieces and an elasticated sport strap for improved retention. Due to the full seal, these glasses are a little more prone to fogging and as such it is strongly recommended to use an anti-fog solution to improve your airsofting experience! The Bollé Tracker II's are available in both clear and yellow-tint versions.