The three antiheroes aren't carbon copies of each other, either. When you swap between characters, you'll see a number of stats flash up on the screen, listing each character's Stamina, Shooting, Strength, Stealth, Flying, Driving, Mechanic, and Lung Capacity skills. They also have a "Special" ability that ties into their personality. Franklin, for instance, is the team's wheelman, and can slow down time while driving in order to pull off insane maneuvers (as you can see in the image above).
Michael's ability is similar to Franklin's, except replace "driving" with shooting. During gunfights he's invaluable, capable of slowing time to turn the tide of battle. Trevor's is the most unique of the bunch, allowing him to go into "Rage" mode. While it's activated, he can take extra damage, deal more of his own, and use a special melee maneuver. Because, you know, Trevor is awesome.