I looked around and saw a few threads about specific photochromic lenses, but I didn't manage to find any about direct comparisons between them. Has anybody owned multiple kinds and been able to compare them first-hand? I imagine transition times are all about the same and none are likely to be great for driving, but which seem to get darkest? How long do they last, really? Mainly, I guess I'm looking for some subjective feedback, which do you prefer, and why?