This reminds me of that discussion between Lucas and Marquand regarding the rebel briefing room in RotJ - the one in which Lucas declared that the rebels were winning because they had the best equipment (can't remember which thread that was cited in - perhaps this one?)

There's no logical reason why the Empire, with their unlimited reach and resources, would purposely field an inferior fighter as an absolute standard - even taking the argument that the first-line flyers are disposable, how come we never see the big guns?

Worse, the idea that X-Wings are just better ships serves to further undermine the whole ethos of the rebellion. As far as the films present the situation (and that's where I personally draw the line), the X-Wing vs. TIE match is at the very least equal, and the outcome of a dogfight entirely depends on pilot skill and courage... and that's the whole point. Or at least it used to be.