In all honesty, there is one aspect where Ford beats Chevy hands down, and that is its Ford Racing program. They offer multiple upgrades and the ability to add components from the Boss 302 and GT500, under a Ford warranty program. If you find a participating Ford dealer, you can have these components installed before taking delivery.
As a Camaro SS owner, I have installed Pedder's suspension, Whipple Supercharger, kook's headers, and way too many others to list. Personally it has been a huge pain in the ass wading through all the false performance claims on the forums to find what works. Some of the mods I have tried, have been absolute garbage. These are mods that were purchased from respected vendors on this site. There is no protection when modding. Not to mention voiding your warranty.
As a GM customer, one request I have is please develop a similar program to compete with Ford. Had the option been available, I would have bought my parts from GM. I will be deployed for the next 18 months. I am keeping my Camaro long term. But when I get back, I am seriously researching the upcoming 2014 5.8L GT500, because of Ford's support of performance mods.
For the OP's question of Mustang vs. Camaro, do you intend to do performance upgrades in the future? If so, I recommend you take a good look here:
http://www.fordracingpartsdirect.com...arts_s/236.htm