I collect for my personal enjoyment and not neccessary for "collectability" or resale value, so I can tolerate some imperfections.
My Kwan from Modelissimo had slight imperfection with one of the decals on the lower lip of the front spoiler. I imagine it was not applied during manufacturing correctly. It was upsetting to see a brand new model with a slight flaw, but at the same time, I knew getting an exchange from over sea on a very limited model would be a bigger headache. I decided to keep the model as is.
On the other hand, I saw a flaw in the paint on the hood of my just aquired dealer version of M5. I took this model right back to the dealer the next day, and they agreed to get me a new one.
It all depends on how rare the model is. If the process of exchange is easy enough, I would get an exchange.