Upgrading from NT 4 domain to AD

Hell-o,

I'm about to upgrade our NT domain to Windows 2000 AD.

Win 2000 Server reskit says that I should pull one BDC offline and promote
it to PDC before the upgrade process.

I just wonder is there any difference if I take the upgraded Win 2000 DC
offline and promote an online BDC to PDC or if I take the Win 2000 DC
offline and put the offline PDC back online if I must roll back the upgrade
process.

What is the main difference between these two actions? I've tested the first
method in my test lab and I've found that this method seems to work well.