Cheers for all the responses and info guys. Keep it coming.
I think the general rule is Mono is better, I agree about the convenience of colour though but I suppose if you are wanting to get the most from it then mono is the way to go. Whatever I go with will likely be mono.
Are the ZWOs and QHYs so good that there is no need to consider anything else anymore?
Again in the interest of pushing things to the limits do other cams perform better.
What about the Ptgrey, ximea and IDS offings which I have heard are pretty good too?