Driving cars/bikes/planes/helicopters, shifting from 1st-person to 3rd-person, holding a wide variety of weapons all at once, purchasing property, cover-system (like GoW), & customizing characters & vehicles (which is FTW :3). But Call of Duty has nice stuff like perks, kill-streaks, being able jump, & a few other things I believe. But overall, I think GTA is more fun & has a wider variety :)