What distinguishes Overwatch from Tf2

Okay so I could write a novel on all the differences from OW to TF2 but that would take way too long, and I'm on vacation.

I'll say though that tf2's casual setting is 12v12 / 16v16 while overwatch is always 6v6. In those 12v12 games team composition and teamwork in general is less important, since I've played games where I've literally carried people to victory with one medic. In Overwatch, it is loads harder to do things like that since 1. There are less people so every character counts, and 2. Losing one person in a 6 man team = much more of a percentage of your team gone than from a 12 man team.

Tf2 also has a 6v6 competitive mode but again, I've seen one soldier be able to just completely demolish the other team (it's not as often but it does happen)

The reason why I hate playing overwatch is because every game is a gamble on if you're going to have fun, since it only takes one person on your team to be a complete and utter moron to throw the entire game, while in tf2 you can have a few idiots.

Which style is better? It's up to you really.