I have read the split domain wiki article.

I would like to know how to make the planning decision of how to assign roles of primary or secondary to a migration where I am going from Exchange 2007 to ZCS 7.0.

Which is the easier path, to have Exchange be the primary, or the secondary? I find much more documentation of Exchange being the primary.

I also don't find notes on post-migration tasks.

For instance if the Zimbra is secondary, and I have finished moving users to it, what do I have to do to it in order to have it become the (sole) primary so I can shut the exchange down?

Just looking for some guidance on planning this out, and which way is going to be the easier path.

Thanks for any clues.