I went from a 125 to a 1200, at the end of the day the fact you are asking the question means you at least have the right idea and understand it needs to be respected. Interestingly, there was only £20 difference in the insurance between the 600 and 1200 when I passed.
The only positive I can see to starting out on smaller bikes is they tend to be lighter so if you do drop it its easier to get it back up, other than that there's nothing that can't be learned on a bigger CC bike compared to a smaller one. I'm personally a quite slow, lazy rider so bigger CC with most of the grunt lower down suits me perfectly as I'm not constantly up and down the box. There's also a lot more fun to be had before the speeds get questionable.
I'm firmly of the belief that if you are the kind of person to go nuts on a bike the engine size has very little to do with the likely outcome, so go try one out and see how you like. I've just bought a GSX1250FA and (Suzuki fanboy alert) I'm really liking it, if you can give that a try too.