One benefit may be that contractors won't be in a race to the bottom, so they won't feel like they should half-ass it. On one of the other websites, they seem

One benefit may be that contractors won't be in a race to the bottom, so they won't feel like they should half-ass it. On one of the other websites, they seem to want to install a spyware on your computer so the employers can see what you are doing at any given moment. I doubt a great coder would put up with that (I'm merely good and I wouldn't) and the odds of finding one there are lower. On the other hand, I think a great coder would be more likely to freelance on a site that has consistent work which they don't need to fight over. So that's my speculation.