which address to use?

[johnny at n0sq.net]

I hope that it's appropriate to post a newbie question here.

I was just reading the HOWTO for creating a DNS server. The HOWTO uses 
internal network addresses. I do have multiple machines but I was wondering 
if it's more appropriate to use the static IP from my ISP?

ns              A       24.223.6.198

instead of......

ns              A       192.168.196.2

??