...The original Defender artwork that was uncovered... the spaceman's head is on the CP side, the finished stencil job, his head is facing the back of the cabinet. ...Was this factory dependent or something?
I don't think that this is a factory variation. Since the change to stencils was made to reduce cost, you have to believe that they'd reduce the cost as much as possible by designing one stencil set instead of a set for each side if they could get away with it.
If you look at some of the artwork images online, you can see the side art presented as one continuous image, extending into the control panel 'bump' in both directions. It's feasible that the one set would have been masked for whichever side was being stenciled to give it a clean edge.
In this case, GameStencils seems to have cheated a little by recreating the left side, then mirroring it to make the right side. By doing so, they'd only have to flip the word DEFENDER around and call it done. That's modern technology.
The result looks really sharp, but as a reproduction, it's not perfect. Ignoring the spaceman, which stylistically could go either way, you can see that the red stencil for the left side art has the upper right edge of the 'diamond' cut back a little to compensate for the shape of the R, but for the mirrored right side art, that ends up behind the D. Although that's not a problem for the D, it leaves the uncut red edge visible beyond the side of the R.
Does something like that really matter? No, but I wish people who make repros wouldn't take shortcuts like that. In GameStencil's defense though, GearHead did say that the stencils were purchased a few years ago, so it's possible that the apparent inconsistencies have already been brought to their attention and researched/fixed.
Now, if GearHead decides that there's just no living with a spaceman that may or may not be facing the 'right' way, I'd be very happy to give the cabinet a loving home. Seems like it already has one though.