The only real advantage are the different colors.
There seem to be as many, if not more flesh colors in the Game line, and one can never have too many flesh colors. They have some different shades of metallics that are unique to the game line, other than that....it is all the same.
As was said above....the Game line is supposed to have an additive to make the paint more durable....whether they are or not....I don't know.
While I carry a few of them, once the ones I have are gone, I probably won't bring them back in as a regular item, but I can always order them from my suppliers for those that are interested.
The Air line is interesting, and offers a side of convenience in that you don't have to thin them to airbrush, just drop them in the AB and go. Also the line has some colors that either aren't available in the Model Color line, or are just slightly different.
Good example is the German Grey, in the Air line, the German Grey is supposed to be a match for RLM 75 (and much of the air line is geared towards RLM colors) where as the German Grey in the Model Color line is quite a bit darker, and more akin to the German Grey you would find on a Panzer.