Major, I am a real stickler when it comes to outline myself. A less than 5% deviation shouldn't be too noticable on the model. More noticable to me are thick non-scale airfoils and wing taper from root to tip. Also a lot of them increase the size of the horizontal and vertical stab. Most "scale" kits for the mass market have a lot of deviations like this and for the average guy its just fine. Competition models have to be done to a higher standard and match the documentation that you present the judges. Again there are many deviations in three veiws from accepted sources. I have at least a dozen Spitfire three views and not one exactly matches the other but my airplane matches the one I chose to use.
So in answer to the origional question I think its matching the documentation as close as possible. Then comes sport or stand off scale that represents the subject closely. Then at the bottom is the kinda sorta looks like it ARFs. Some of the ARFs out there are really awfull looking but they sell a lot of them because a lot of people are more than happy with a plane the resembles something scale. Remember the majority of flyers don't have the building or flying skills required for an exact scale model. Don