anidb.info has some fansub comparison, but no screen shots. If you go to a series's individual page (and usually AnimeSuki is kind enough to provide the link), you can look at all the groups that are subbing the series and see comments from users about them. Of course, these comments can be dumb/uninformed/fanboyish/biased, but you can usually get an idea if multiple people say, "Too many grammar errors," "Ugly subtitle font," "large filesize, but bad quality."
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