Agreed that there are issues with NIB - on the other hand, new pins are a lot of fun to play, generally with deep software and many of the out-of-box issues get address by the manufacturers along the way (and software upgrades too). As expensive as they are, with the size of the runs more perfection and polish would make them even more expensive and unaffordable.

Old pins were made to make money on route and the list of know issues on them is very long (e.g. lack of fuses between the transformer on Williams System 3-11 pins = fire) Playfield pooling is frustrating and hard to fix, as well as the other issues mentioned. However, often the manufacturer is making some of these issues right. For example, Stern replaced the easy to break Herman plastic breaking on Munsters for free with a bracket protector.

Buy used (and pay more most likely), put a NIB order in and wait and take your chance on playfield issues, go play on location if you are not sure, but don't avoid these new pins because the value might drop due to playfield chipping, dimples, scope wear, etc.

Perhaps a just as good of a question as initial quality is how does the manufacture continue support after the sale?

In that case I would rate them as such (my personal opinion only):
Top three:

American, Spooky and Stern
Edit: Left out CGC - also pretty good customer service I understand
Good start - Pinball Brothers with Aliens (not much history and some initial quality issues but very responsive so far)

Not as Good - JJP (lost of LTG was not good IMO).

I do not have any personal experience with Dutch Pinball, Haggas, Metamorphic so I can not comment on them, perhaps someone else can.