In my opinion it's all plastic model and must be seen like this, of course that you can take some point in consideration but.. what would you do in the scenario above:
You have two categories, A and B.
On the category A have 4 cars, amazing cars all built with lot of PE, amazing paint job, perfect fitment and so on, but only 3 cars can win, and the decision is very, very tight.
On the category B you have only one car, hand made, out of scale, crap paint job, a.. bad car.. but.. you have to give the 1st prize to it, why? simple, because it's the only one on it's category.
Do you think that it's fair?