It's weird how so many people play Overwatch but not a lot have heard/played Battleborn even though many considered Battleborn to be better when both games were announced. I've only heard a few people talk about Battleborn in my school.
It all comes down to preference. Battleborn a lot more similar to a MOBA than Overwatch is. Battleborn relies and longer term strategizing with fights more spread out around the map. It has a higher learning curve than Overwatch does but being similar to a MOBA, it is also slower paced. Overwatch is a lot more similar to other fps games relying on strategizing on the spot. Faster paced and easier to pick up.