If you're talking about Unity and Godot, the main difference is that one tried to scam their customers by unilaterally changing the terms of contract and requesting an asinine amount of money based on downloads (not purchases) of games made with the engine, without even having a system in place to keep track of them.
The other is Godot.
Seriously. Why do gamers spend thousands of hours on games they hate. Life's full of shit to do. Go play something else. Or, God forbid, touch some grass. Why waste the little time you have on earth doing something you don't like.