The majority of it is personal preference. That being said, I prefer Chevrolet for a number of reasons. The first is Fords are butt ugly (debatable, but not with me). The second is that GM parts are more universal and the repairs are cheaper, and I have always found them more reliable. This is a hotly debated point among those who don't work on cars, but among us technicians, the vast majority will thank Ford on a daily basis for keeping us working. There is also more performance potential in Chevrolets. Fords have weak engine blocks, and poor head design to state a few reasons.