The photochromics work well on the road but on the trail (mountain biking) they don't change tint as fast as you're dipping in and out of the shade. It can cause the trail to suddenly appear too dark when riding at speed.You want the glasses you purchase to fit well i.e., not slip down your face when leaning forward in the cycling position. That happened to me with Oakley Flak Jackets. I bought the smaller Half Jackets, and that cured that problem.Also, you want the glasses to sit high enough on your face that you view through the lenses and not into the top of the frame when you in the cycling positions, particulary in the drops. The only way to test this reliably is with you, the glasses, and the bike.I can't make any recommendations for you; there's a whole world of glasses out there at all price points.
I had Nashbar photochromics for about a year until they got broken. I bought them because 1/2 of my riding is during dawn or dusk (commuting). Not great, some double-vision shadowing when at their lightest and not light enough to wear in very low light, and they didn't get that dark for sunny days. Bought some Tifosi's last year. Much better. No shadowing, far greater range (almost completely clear, work great in very low light), not super dark but still ok for very sunny days. About $60 on sale.
The most important qualities to look for in a pair of new cycling sunglasses are the clarity of vision the lenses provide and the protection they afford. Hazards such as grit, insects and overhanging branches can seriously damage your eyes when you're hurtling along at 25mph or more, and even rain can really sting your eyeballs. half-rimmed sports sunglasses with small nose pieces and tough lenses are a good example of cycling sunglasses.The smaller the nose piece, the better, because combined with a half-rimmed style, your peripheral vision is clear to see what's in front of you and those crazy right turners to your left.