A:Honestly? None of them. And I know exactly what you want, as I do a fair piece of mountain biking around Port Townsend, WA, and were often riding in and out of sunshine. Thats even more of an issue in sunny La Grande. If youre making pretty quick transitions from sun to shadow and back, the photochromic glasses out there just cant manage the switch fast enough to do you any good.
And that can be dangerous. Several years back a guy in our group was wearing tinted lenses while biking with us on Gold Creek, a trail in the Olympic National Forest. One especially exhilarating stretch of trail side-hills a very steep wooded mountainside. Youre also descending, so a moments inattention or distraction can be dangerous. Anyway, he got a little bit blinded going from sun to shade, off the trail, yadda yadda yadda, broken collarbone and concussion. Ouch.
For that reason I usually stick with clear lenses for mixed conditions. Those, or yellow lenses, which add some contrast in the shade.
One possible option: Rudy Projects RB3 glasses ($175). The flip up in a single motion, so you can easily get yourself more light. Lenses in different colors also can be used. Probably about as good as it gets for tough riding/lighting conditions.