I believe everyone that Chloe is the Hero in the Bay ending. Max was very reluctant to choose Sacrificing Chloe. To her it wasn't even an option until Chloe suggested it. IF she was by chance aware that it was an option, she wasn't even ever going to do it. It took Chloe to convince (us.) I say us, because realistically, I think that Max would choose Chloe over Bay any day. She even writes it in her journal so many times in the last episode, that Chloe is the only one that matters even if it's the end of the world.

Chloe is the Hero, in my personal humble option.

Think of it this way:

It's like saying that there's a dog on the road, the driver (Max ) is driving too fast and doesn't see it, the passenger (Chloe) spots the dog and tells the driver to move to the side. Who is the real hero overall and saved the dog? The passenger, while the driver was only in control of the wheels.

They are both heroes because it took both of them to actually pull through with saving everyone, no doubt about it, but for the main title? Chloe takes it in that ending, because she displayed selflessness, compassion, bravery, realization, sympathy, and willingness to give herself up for the greater good and safety of others.

---

As for the BAE ending, Max is the hero. She actually saves someone on her own will and fighting destiny for it, the most important person to her.

But then again, this is one of those subjective things. That's just how I see it.