Well I think that Whitney winning wouldn't really make a difference. Hardly anyone takes America's Next Top Model seriously because no winner has ever went on to great success in the fashion industry. The show doesn't even focus any attention on physical fitness. Australia's Next Top Model emphasizes the notion that the girls need to be a certain size and be physically fit in order to get runway work because no designer would want to hire a model who has "bad" (I use that word loosley) proportions. I remember Saleisha used to have the unmodelesque proportions of 32(?)-26.5-37.5. Most models have proportions like 32-23-34 or 33-24-34. As ridiculous as the latter measurements may sound, those are the measurements that get work. So in terms of working on the runway or in the fashion industry in general, yes, Saleisha along with many other contestants on the show America's Next Top Model needed to "check [their] thighs in the mirror." I think this "choosing a winner to represent the average American woman" is just another stupid thing that Tyra did to make herself seem like a saint. What should really matter is how good of a model the contestant is as opposed to their missions or their messages or their personalities or the portion of the American population that the contestants represent. In the fashion industry... hardly any of that matters.
I'm not necessarily saying that skinny itself is perfect, but skinny is what's generally considered perfect in the fashion industry. Crystal Renn is widely known as one of the more successful plus size models, but what has she done throughout the past year? Her nymag model profile has nothing listed for the past year and she never landed the cover of a Vogue whereas the marginally thinner Sophie Dahl (who was also considered a plus size model at one point) has gotten three British Vogue covers and an Italian Vogue cover. So no matter how much we try to convince ourselves otherwise, plus size models are just not going to be successful in the mainstream market right now no matter what kind of message Whitney's win is conveying.