Well I decided on the 5D due to having used one, I love the images it produces and they do have a rather distinctive look to them. Also, I know people who shoot Canon that while I’m raising funds for my own lenses can lend me lenses from time to time for motorsport etc, and seems as I’d have to sell most of my gear to fund it anyway I might as well go all the way and jump ship seems as I planned on doing that long term - Canon’s lens lineup seems to have a nicer range than the Nikons, although that could strike up some controversy.
Strictly speaking the D600 is a better camera per say. But the 5D seems a safe choice seems as I’ve used one and loved it, plus I do prefer the big pro body ergonomics to the semi-spo bodies. But anyway, I think it’ll be a worthwhile upgrade, the main downside at the moment is that I’ll only be able to afford a 50mm F1.4 to go with it, which isn’t too bad seems as it’s my favourite lens at the moment.