Generally speaking, the faster the computer (processing wise), the faster the export. This is bit bit simplistic in that there can be other factors depending on the sequence. But generally speaking this is the caveat that is steering me to a custom built PC from ADK.
Tom Daigon
PrP / After Effects Editor
http://www.hdshotsandcuts.com
Mac Pro 3,1
8 core
10.7.3
Nvidia Quadro 4000
24 gigs ram
Maxx Digital / Areca 8tb. raid
Kona 3