For reference, ACS vs. Zope was discussed some time ago on this bboard--here's the link (note that by now both toolkits have no doubt evolved):
https://openacs.org/bboard/q-and-a-fetch-msg.tcl?msg_id=0000Dl&topic_id=8&topic=OpenACS%20compared%20to%20other%20toolkits%20and%20technologies
