I bought a used 2011 z71 Crew cab a year ago. At the time, I test drove it and an F150 ecoboost 4x4 in SLT trim, same year model, but double the miles. The Chevy had 14000 when I bought it and the Ford had 30000 at the time. So similar trims and year models yet the Ford was still several grand higher than the Chevy. Ended up going with the Chevy because of price and lower mileage.
Like many have stated, even with the v6 ecoboost, the Chevy 5.3L still gets better gas mileage. The turbocharged v6 in the Ford was noticeably more powerful, however. And comparing those two models, the Fords interiors are much more spacious and nice, even in the cheaper trims. The Platinums and Lariats are such much nicer than the loaded out XLT Chevy's it's not even funny. However, I believe the new 2014 GM's have considerably evened the playing field when it comes to interiors. I've always thought Chevy's are better looking on the outside.
Looking back, I'm glad I saved myself a few pennies and got a "newer" used truck. The previous owner was an elderly man who left it in pristine condition. I loved the power of the ecoboost and the Ford's interior better, but I would make the same choice if I did it over.
I've got a good buddy who is a die-hard Ford guy. He's had a 2007 F-250 Lariat, and multiple newer body style F-150's loaded out. Never owned a Chevy in his life, but when talking to him he said I made the better choice in the long run.