If you are curious you can try the lower resolution with scaling to see if that makes a difference. If the performance gain isn't worth the graphics quality drop, then you don't have to test it that way for my sake.
Personally, with my monitor I can not see a difference between native resolution or lower (probably more to do with me than the monitor). At the highest resolution I get some minor background jerking when running, in regions with lots of stuff on the screen. I didn't try tweaking any graphics settings, since dropping the resolution a notch fixed it without a quality drop, as far as I can see.
