A little more stability due to longer wheelbase.
Gives clearance for big ATV tires.
Increases rear suspension travel.
Decreases rear stiffness i.e feels like as softer spring is installed with longer travel.
Good opportunity to install sealed swing arm bearings in lieu of hard to install OEM seals and bushings.
Can improve hill climbing ability.
Allows more mud, water, debris to be tossed up past rear fender.
Increases turning radius.
Brings tire closer to rear of rear fender ( not a conflict issue with a 2" extension).
Makes wheelies more difficult.