Okay, here we go:
Vintage Chaos has more spices and agarwood right from the start. The agarwood is especially prominent and absolutely addictive to me.
The new Chaos' agarwood is almost completely lacking by comparison. The beginning is much sweeter, like candied lemon/lime citrus. It's rather heartbreaking to me when these are worn side by side. Vintage Chaos does develop some sweet citrus as it progresses, but retains more of the spiciness that is similar to that found in Black Cashmere. However, where BC is (say) a 5 on a 1 to 5 spicy scale, vintage Chaos is a 3 and new Chaos perhaps a 2. It's really difficult for me to get past how much more of the sweet lemon/lime is present in new Chaos versus than the old. It seems to get in the way of allowing the new version's notes to come forward fully and represent themselves more like the old. Most disappointing is that thru the development, new Chaos never matches the agarwood note found in the vintage version. It's there, but has a very minor role comparatively. That said, I do enjoy new Chaos on it's own. The spices, herbs, and other woody notes are very similar to the original, just toned down some. The fizzy cola note (that Nukapai so aptly describes in her review) is about the same, and may even seem more apparent due to the increased citrusy sweetness.
Longevity is definitely affected. After a few hours, the new Chaos smells like a glass of coca-cola with lime and melted ice (i.e. watered down). Vintage Chaos sits more closely on the skin, but remains true.
Now I'm going to pretend I never did this side-by-side, and go back to enjoying and wearing new Chaos. I hope.