This article has 10 reasons in favor of Fortinet, I would recommend them but I am not very familiar with Cisco's solution.
http://www.itgweb.com/blog/the-top-10-reasons-to-choose-a-fortinet-next-generation-firewall
As far as dollars per protection, I would say Fortinet is your solution. I found this article pretty helpful: http://www.itgweb.com/blog/the-top-10-reasons-to-choose-a-fortinet-next-generation-firewall
