I agree with @apoorv020's post, but think it could be expanded upon.
Having read both the Hollows, and the Dresden Files, one of the biggest differences (in terms of human-vs-supernatural), is that in the Hollows, the supernatural denizens are public. Everyone knows there are witches, vampires, werewolves, etc, whereas in the Dresden Files, they are highly secretive. The general population goes out of their way to ignore any attacks or weird occurrence, with the authorities always willing to find an excuse for things ("it was a gas leak/biker gang/escaped zoo tiger") that do become public.
And yes, there was a major population difference - in the Hollows, after an epidemic wiped out nearly half of humanity, the witches/werewolves/vampires, etc, came out of hiding, to the point where they had (roughly) equal numbers. In the Dresden Files, most of the supernatural world is also predatory (unlike Hollows), with two different types of vampires (Red and White court) being the most prevalent. As predators, their numbers are much lower than their prey animals (us :) , or it would be harder to keep it a secret.
The Hollows denizens, being mostly witches and werewolves (vampires were a much smaller percentage), were benign, and could co-exist with humans in large numbers, once they became public.
Also, one of the reasons Harry is well-known, he's the only wizard who actually advertises in the Chicago Yellow Pages. :)
Spoiler update from the book "Changes":
The Red Court is now dust - the spooky-side population dropped dramatically (and it was very dramatic...)