How to organize the back-up.

[AM]

Hi folks,

just a tip on how to configure the slave servers.
The scenario is the following:

company A and company B

each company has got its own domain names and has one master server and the respective slave.
Now the boss asked me to make the backup of all the domain names belonging to the company A on the company B servers and 
vice versa.

So, the company B master will be the slave of company A zones and vice versa.
What would you suggest for the slave servers? I mean, should the company B slave take the company A zones from the 
company B master or directly from the company A master?

I'm sorry for these newbie questions but I'd like to know if there are any advantages on having each slave to take all 
the information from its "first" master instead of getting them directly from the master that is deputed to manage the 
zones. I could think of that scenario if the bandwidth between the two company is very low.
I will appreciate any of your explanations on this topic.

TIA

Alex.