With the vast experience of an entire weekend of digiscoping behind me - and that a weekend of rain and bad light in the Australian winter - I am eminently unqualified to answer your question, Andy. From what I've read here, I would guess that the optics are more important, but I hasten to stress that that is purely guesswork and that others much more experienced than I am will doubtless weigh in with their knowledge.
However, one thing I say with confidence - even though you have doubtless worked this out for yourself long since - is that from the point of view of chosing your equipment and deciding how much to spend on different parts of the kit, the scope is much, much more important. I bought a scope and a camera last week. (ATS80HD & CP 4500.)
I'll have the scope for ... who knows? 20 years maybe?
And in perhaps two years time I'll walk past a camera shop and see a camera that costs $500 (i.e., less than half of what the 4500 cost), has 12 million pixels, 10X optical zoom, a comprehensible menu system, the on-off switch in a less stupid place, zoom controls that fall neatly under the finger, and an LCD screen that is bigger than my thumbnail. Oh, and a standard battery life of 8 hours.
Well, it will have about half of those features, anyway - and I'll buy it. What I'm getting at is that it makes sense to get the very best scope you can stretch to, and if you need to economise, economise on the camera, because you will more than likely be buying a new camera in two or three years anyway. The scope, on the other hand, will last you half a lifetime.