I made some tests running 3D platformer on my rig, it runs faster in Godot 3 with real time reflections, while it is slower in Godot 2.
Why is Godot 3 so faster, even with new graphics enhancements ?
Did you notice the same performance gap without the real time reflections ?
Just to know if it's specific to this feature.
A re-written renderer using a far more modern GL API if I'd have to wager a guess. Can't test though Godot 3 still doesn't run on Windows for me. edit: to be clear I'm sure the new renderer is better optimized in general.