Actually I disagree guys, Falcon23 got it right.
I got my first clue into this back in 2002 at the AH con. Was watching Drex get ready for the 2vs2 champtionship. One of the things he did was turn his screen res from 1600x1200 down to 800x600.
On the same screen, same monitor, at the same distance, planes are now much larger.
Gunnery is done on your FE, so what you "see" is what you hit, is what gets sent to the other guy.
Now granted most don't like flying at 800x600, it doesn't look as good.
But rather than cranking screen resolution to the max you might want to look at keeping it low.
Changing screen res from 1600x to 800x would quadruple the enemy plane sizes. Making them much bigger targets.
Typically I run 1280x720. And would probably drop it to 1024 for a duel.
Texture size doesn't come into it at all.
Try it for yourself if you don't believe me.