Online seems way bigger, for example can fit a tracker to your car and it shows where you parked it but if you park it just anywhere police will impound it.
Can also buy insirance and claim if another player steals or damages your car (invest shares in the insurance company). Seems alot more options for guns, more camos etc (invest in ammu nation, shares will only rise as players will constantly buy). You then get jobs which you can do alone or as a team. Some jobs will also be competing against other teams.
Can then have deathmatches, races etc etc
There is a whole load of extras.
I just left mine at the loading screen last night and went to grab some dinner. Got back to the xbox and i was in the race against lemar but obvs lost. You then have to go through a tutorial doing bits but that doesnt take too long
Once your in the free roam with other players its fine, couple of times when i tried to load a mission or something it would get to the loading screen and freeze but just re-join the game in progress