I am making this statement because I feel the arguments used against Donkey Kong, and Donkey Kong Junior do not apply to Donkey Kong 3.
First reason is Donkey Kong 3 even in mame 106 has near perfect emulation. To be honest I have never seen a difference in any way shape or form. The other two games do have some sound issues.
Second reason is unlike the first two in the series diagonal control has no effect on gameplay. In fact if you are using keyboard you will have a harder time playing it than joystick.
Lastly, I have heard they made 5000 machine kits. Not sure if that number is accurate but it seems about right. Donkey Kong had 130,000 machines made, and Donkey Kong Junior had about half that made. So while DK3 isn't exactly rare it's definitely harder to het to.
So when it comes to all the scores at marp and Twin Galaxies I view them the same way I would an Arcade score.