Windows Time Service - Reliable Time Source

Greetings,

I'm looking into configuring Windows Time Services for our domain.  There are three lines of thought that I have seen:

1. Configure all domain controllers to point to to internal NTP appliances that we own.
2. Configure the PDC emulator as the reliable time source and point it to these NTP appliances
3. Configure the PDC emulator and one extra domain controller as reliable time sources (for redundancy).

I have found arguments for and against each of these.  The general Microsoft stance seems to be that (2) is the way to do things.

How do you configure your time?  How would you recommend we configure ours?  I am leaning towards (2) given the preponderance of Microsoft documentation pointing to this, even when mentioning internal NTP appliances.  Your insight would be greatly appreciated!