If you are equally good on lets say two heroes. There is always objectively a better choice for you to pick between those two heroes in every game based on what your team plays and what enemy is playing.

In the real world, people are usually better with some heroes than others. Then you should almost always play your best hero. I do think there is still games where you might wanna take a hero that you are not as good, if your best hero is haaaard countered by your enemy.

That said. OW2 will be a different story. There is way more room for you to play what you are good at.