SEP Domains: Single Domain vs Mult-Domain

I am trying to find a good list of the benefits and downfalls of creating a single SEP domain vs multiple SEP domains.  Anyone have a good reference document for helping to make this kind of decision?  We are trying to determine how best to setup an environment and are considering the following options:

Option 1

• 1 SEP Domain (Entire Company)
• 4 SEP Sites (3 Geographical, and 1 Logical/Administrative)
• 6 Active Directory Domains (3 Geographical and 3 Logical/Administrative)
• 6+ SEPM's (1 or 2 per SEP Site, depending on needs)
• 20,000+ Clients

Option 2

• 4 SEP Domains (3 Geographical, and 1 Logical/Administrative)
• 4 SEP Sites (3 Geographical, and 1 Logical/Administrative)
• 6 Active Directory Domains (3 Geographical and 3 Logical/Administrative)
• 6+ SEPM's (1 or 2 per SEP Site, depending on needs)
• 20,000+ Clients

Option 3

• 6 SEP Domains (3 Geographical, and 3 Logical/Administrative)
• 6 SEP Sites (3 Geographical, and 3 Logical/Administrative)
• 6 Active Directory Domains (3 Geographical and 3 Logical/Administrative)
• 6+ SEPM's (1 or 2 per SEP Site, depending on needs)
• 20,000+ Clients

I'm fighting political battles with regional and AD domain admins in an organization while trying to implement a global delivery model.  I need some good solid advice on the advantages and disadvantages of creating separate SEP domains.  I'd like to be able to compare what the real benefits are of choosing any of the three configuration over another.