I think it's a REALLY close call. In theory, twice as many cores, faster bus speed and faster core speed (just a nudge, really) I actually expected a bit more. One of the things I did not mention in that review though was when I loaded up the project on the 4 core, the render bar was red and it would not play before a render.
On Angus, the render bar was orange and it played RT just fine. Probably that fact alone (the additional level of interactivity) might have prompted me to sell the BigMac and buy the Angus. When you have unreasonable deadlines - and who doesn't... That additional boost can make a real difference.