I've worked with both and initially preferred the Dogma but over the last two years have started to favor the C59. I really like how it fits people, I find it to be lighter and there is no significant loss of stiffness; the ride quality is wonderful. The Dogma is a heavier bike but that extra weight pays back in stiffness and responsiveness and at the price point most owners build them up with such light weight grouppos, weight is not an issue.
I like to see people make the decision based on optimal fit but of course aesthetic plays a part. I think the look of the C59 is timeless, the finish of the paint and the badges are perfect and overall I think you get what you pay for. The Dogma is extremely flashy, a bit of a long fit and I think is either hit or miss as far as aesthetic appeal goes. If it was me, I would go with the Colnago, 10 years down the line and a fresh grouppo and wheel-set will make that bike look as appealing as the day you got it.
One other thing I like about the C59 is the option of sloping geo, which from my experience gives many riders an even better fit.