More weight on the front for better steering.
Less likely to wheelie.
Less twitchy in a slide.
Slightly better geometry across the full range of suspension travel (not so convinced that this is more a theoretical improvement than a real one).
Most old Yammies handle better with a longer swing arm. Yamaha had this stupid habit of making a new model with a short swingarm, and then extending it the next year (YZ125C vs X, D vs E, etc). In every case, the later model clearly out handled the older version.
