Being that the language is so new and not thoroughly tested, Can you just create some test to determine what is faster?
I suspect that DrawRect is faster than Drawing a bitmap since each pixel is not scanned for color content.
I usually don’t test to see which is faster but just test if what I am doing is fast enough for my purpose. if it is, I stick with it else I find an alternative if possible.
On my game that I am making “Mission patrol” I use DrawPoly and is fast enough to draw all of the backgrounds of the game so I never bother to test if drawing images is faster.