I don't like these models either, not because they give an advantage (No wonder some people are so good) But because they are no where near historically accurate, And I hate Pure Mode because I use nothing but custom skins and sounds. Every weapon I have a custom skin, The players I also have a custom skin for, and every sound effect, from bullet impacts to gunshots to magazine changing... I wouldn't really say bright red and bright blue skins give an advantage myself, as cranking the brightness to max will do the same thing, But I'd much rather prefer realistic 2nd Rangers and Waffen SS over Red and Blue silhouettes
Some models and/or skins just make the game feel completely different, and for the better in most cases, I used a custom Thompson model that I liked so much from beta 1.2 all the way until source was released, The animations didn't work after beta 1.3 came out, but the model itself looked and felt better than any other, MGs weren't even put into the game yet until 2.0... anyone remember that serious lag problem 2.0 had after a round was won? *cringe*