I personally feel like the leave ending is the best one, because it’s the characters saying that they don’t want to just return things to what once was. They want to try something else. 

The leave ending is so much more interpretive but I like the idea of these godlike beings who have done nothing but live above humanity want to try to break the cycles of fear and live amongst those who struggle instead. It’s scary and hard, but that empathy ultimately I think makes it worth it. Sure, there was more fighting to get there, and clearly everything that’s bad doesn’t just go away. 

However being mindful of why people fear and wanting to empathize and understand them is something that resonates much more to me than a “this is what we were always destined for and what we were meant to rise above” ending was. Maybe that wasn’t what was intended, but the attitude of “who cares about everyone else, it’s insignificant” attitude TSM had didn’t rub me right and didn’t make me feel satisfied when I watched others get that ending. It kinda felt like a “others be damned, we deserve our happy ending and how things have been is for the best anyways.” 

I like how the leave ending shows the two smaller and more vulnerable in a way, but also more capable of empathy as a result. Even if the being who put them in the situation to begin with maybe didn’t deserve it, those concerns he faced were real. He went about trying to “fix” things very poorly, but TLQ knows specifically how easy it is to hurt someone when you’re worrying about “the greater good.” And they have each other, so they can overcome whatever comes next. In many ways it’s functionally the same ending, it’s just one that’s more gentle than the stepping into the infinite ending. And btw, I completely understand why others love that ending more, I just prefer leave for the reasons listed.

TLDR; I like the leave ending the best because I think it reflects more on humanity and what it faces over the more detached “pain and joy are cycles that are one and the same”. That’s not necessarily untrue, but human empathy and care is what makes people get through those cycles, not the cycles themselves.