I just want to know which would be the best CMS for a Social Networking Site.. Is it Joomla or Drupal..?

u gotto search plugins for both the cms in order to suit your requirements .
There are community builders for joomla AFAIK , aint have much idea about drupal .

I think Joomla is better than drupal.Becoz ... Lot of Templates are avilable for that.

In my opinion, WordPress, Drupal and Joomla are too bloated and confusing for the end user to edit. My clients love Concrete5, which uses simple in-context editing and point/click/drag all wrapped up in a shiny interface. It’s easy for developers to extend and easier for users to work with. Try it at http://bit.ly/concrete5cms if you find yourself spending large amounts of time training and supporting your clients on one of the bigger systems.

You should try WP! It's really easy and cool, but considering your question, i would choose drupal

i think drupal is awesome but joomla! is simply the best.
Joomla is much nicer in design

i think joomla is best suited for this