I always pre order and have not been disappointed. I get what I want at a discounted price, but I'm also not a rivet counter and if something is a little off I don't get upset, after all, it is three rail "O" gauge.
If I were very concerned about exact detail, color and model type I would be modeling in "two rail scale" or HO.
Everyone wants museum quality models , but at five and dime prices and that's not going to happen.
So if your a person that is very particular then do yourself a favor and don't pre order, wait till the item is released and find a LHS where you can examine the finished product before you buy.