Toyotaboy brings up a good example:
Pins usually have a different art style on the PF than the rest of the art package. It's super evident on early 90's Data East, most of the 90's B/W, but became less obvious once we got into the modern "Photoshop Collage of Stock Images" age. By "PF art" I mean posterized, simple colors, outlines on most everything, no shading.
If you look at the "gold standard" Metallica the entire game is done "PF" style. Zombie Yeti's art style is also "PF art" making his games look cohesive. Even AMH... some say "it was bad, but better than RZ" well again, that's because it was in a more traditional PF style - simple colors and outlines.
Alex Horley does not paint in that way. So while the BG and cab may be what "everyone wants" applying that style to the PF isn't as universally loved. Because subconsciously we're used to a different look.
That said, I agree it could use more detail. As-is it doesn't match the density of the rest of the art on the same machine! I can't speak to that decision, only Chuck can.
I can however speak to my flow art and inserts. I wanted the inserts to "pop off" the background, almost like a 3D effect. Most inserts are just white text, black online, straight font. I wanted energy, and a unique look for each mode light (staying within the "3 font rule" of course) They have a bold, lurid, comic-book feel I knew Rob would like. We could desaturate them to fit the background better, but they would look worse when actually lit (washed out)
Shot trails - well, they're hand-drawn at least! (Wacom) Alex had trouble visualizing them (first pinball!) so we considered them part of the "insert layer" and added them ourselves (with Alex's approval) Unlike the inserts, I believe we could tweak their saturation to blend into the background better.