The cage length effects the tooth capacity of your drivetrain, long cage having the largest capacity, basically dictating which gear ratios you can select. Short cage deraillers are a little lighter (barely), and I should think are marginally less likely to strike rocks etc, but I've always used long cage so I don't know which is actually better. As for whether this years sram stuff is better than last years, I have no idea, haven't used it, sorry.