Windows server 2008 DNS Problem

Hi
I am Doni Agna Lourdu. I want to know the difference between the following senario.

Recently We have hosted two Domains on our newly boughted server(win 2008).
I hosted according to fourns in www.iis.net. I was confused in New Host (A or AAAA) creation. Below I have given two scenario.

While DNS hosting ( Zone Lookup)

My System Name : iserver

Scenario I

Host( Uses Parent Domain if blank) : www
FQDN : www.mydomain.com
IPAddress : 19.56.72.13

Scenario II

Host( Uses Parent Domain if blank) : iserver
FQDN : iserver.mydomain.com
IPAddress : 19.56.72.13
Note : iserver is my server name.


Please give me the difference between two.

Looking for favor.

with regards,
Doni Agna Lourdu. M