"In reality if the people producing the DVD don't screw up...there should be little to no difference from DVD to DVD."
It's not a matter of "screwing up". Different companies use different recording/mastering/authoring equipment and software. You can't help but have differences. Not to mention the fact that none of the people on this forum use all pro-level equipment in their transfers to begin with. The only person would might have come close was Editdroid, since this system was designed by Lucasfilm, and later became AVID. Of course, this is *only* the editing software.
Regardless, you can't reasonably expect home-made DVDs to automatically be of the same quality as those of major labels.
What you describe would be a nice scenario, but it's far from reality.