Better to use multiple networks?

Afternoon everyone.
I was doing some testing on one of my sites and noticed a large different in the number of impressions vs number of unique visitors to my site. About 10 to 1 for impressions to visitors using adsence.
I was wondering if people saw a better increase in clicks using different networks for their ads, or if sticking with 1 network works out best.

See original post by urbn