Thanks Nate!. Today nightlies had the change, so I did some tests with the same scene, same conditions (drawing only quads, same quantity of actors, etc)...
And the results were really good! Using SpriteBatch for gui, and PolygonSpriteBatch for the game scene (which draws spine skeletons, simple sprites, particle effects, etc), the performance wasn't really bad - only like 1 or 2 fps less in a really crawled scene. It isn't noticeable, so I will leave it like that and start experimenting with FFD.
Thanks again for your work, both of you 😃 (Nate and Shiu).