You have no advantages when using Zope :)
Remember that these forums are not a marketplace - we don't really do bids and tenders here (not in the first place at least).
Also only few people here have experience with Zope, but loads with OpenACS. I'd expect some bias...
To help you at least a bit, you should give us some information.
How many people are going to use the intranet? OpenACS generally seems to be a bit more involved...
Which of the oodles of Zope products do you intend to look at/use?
Do you want to develop new functionality?
Do you want to use Windows for your server? (Then forget about OpenACS alltogether)
Which database?
