All three games, Overwatch, BattleBorn and Gigantic cover different specific genre’s and split from each other, with Gigantic and Overwatch being the closest of the three. From people I know who have played all three titles, this is my general breakdown.
Overwatch: If you’ve played Dirty Bomb, this game is going to be very similar in objective style. The whole idea of the objectives are the same, on top of that the whole concept of characters being different and having their own unique set of skills and weapons is also shared. However, there is one distinct issue with Overwatch right now that needs addressing, and hopefully does get changed. It feels SO SLOW. Like, it’s not even funny how slow the gameplay feels, which does not feel addressed with how the ‘Gameplay’ and ‘Character’ trailers are done. Abilities do not one shot like every trailer shows, and due to characters not having any kind of movement ability unless built into their kit, everyone moves so slowly. Those who do have movement in their kit feel great, but kind of at a disadvantage having lost an ability spot for movement. Fix this and you have a game WAY better than Dirty Bomb, as Overwatch has ‘Character’ built into the game and will probably sell on Blizzards title alone.
BattleBorn: As someone said, it feels very grindy against hordes of enemies. More of a MOBA feel to the game, especially with the use of the enemies. Hopefully the game makes the balance of PvE enemies and PvP enemies correct, or it will feel pretty boring just mindlessly killing small enemy bots over and over and then never really killing much in the way of actual people in real, exciting combat.
Gigantic: The closest one to a MOBA, as it practically is a MOBA port to an FPS. The whole system of abilities is being moved over, as well as the idea of a MOBA style laid out map and the balance of enemies to players seems to match that of a MOBA too.
Overall, I am looking forward to Overwatch the most, and look forward to casting for this game too. Battleborn is the one that excites me the least actually, the whole grind gameplay looks terribly boring to cast and watch, with Gigantic coming a close second to Overwatch.