What is the difference between create secondary zone via Zone Transfer and External Secondary?

[#1]

Hi,

I noticed that in attempt to create seconday zone on our Microsoft DNS Server, we could used two ways:

1) Enable Zone Transfer on Authoritative Zone in Infoblox, set "allow zone transfers to" secondary Microsoft DNS server IP in Infoblox, and create that zone as secondary zone in Microsfot DNS in order to pull the zones records from Infoblox.

or 

2) Under Name Servers tab of Authoritative Zone in Infoblox, set External Secondary for Microsoft DNS server IP, and create that zone as secondary zone in Microsfot DNS in order to pull the zones records from Infoblox.

Both is working well in creating secondary zone on Microsoft DNS server. Hence, from infoblox perspective, is there any difference between using zone transfer options and external secondary Name Sever?

Thank you very much for your opinion