What do the stats in Jet Set Radio Future do?

Stamina is health.

G-stamina is how much graffiti the character can take in Tagger's Tag mode.

Spray is how many spray cans they can carry.

Graffiti is how fast the character can spray each graffiti point on a medium, large, or extra large tag.

Acceleration is how fast they get to top speed while on the ground.

Cornering is just how they handle turns.

Grind is how easily they latch on to grindable surfaces.