My short answer

is that if you want a plug-and-play site, then Joomla is the better choice in terms of ease of setup, choice of addons, etc. An expert will be able to use either well in the entry level space, but the novice (aka, usually meaning the customer) will find Joomla much easier.
In terms of choice and ease of customisation of templates, Joomla wins hands down.
Drupal's sweet spot, in my opinion, is where you are constructing a customised web site solution with very specific goals in mind (you are trying to create the next YouTube or Basecamp). But having said that, Joomla competes equally well with it in that space as well so either is a good choice.
Culturally, and as a generalisation, Joomla tends cater more for the needs of the user (while making life easy for the developer), and Drupal more for the needs of the developer. What that means is when we do an upgrade, we like to keep things backward compatible to the last version as much as possible. Joomla's culture is also geared toward commoditisation of extensions (we are more like Apple) whereas Drupal leans more towards implementing whole, custom solutions extended from the base product. Neither is necessarily right or wrong, just difference approaches. The end result though is that Joomla's market starts at the very bottom of the pile whereas Drupal starts a bit off the bottom (and for comparison, you need a ladder to get to where Typo3 starts).
That's my opinion but for empirical data we can look at the SXSW shootout between Joomla, Drupal and Wordpress. While the judges did not have the courage to call anything but a tie (rimshot), it was clear from the evaluation criteria that Joomla was the best system. Certainly it stood out as taking the least time to build (aka, best productivity score).
For your site examples #1 is definitely Joomla's sweet spot. For #2 you want to be looking at Kunena for a forum based site and probably Jomsocial for a social network. For #3, there are many commenting systems (shameless plug:
jxtended.com/extensions/comments.html) and you've got plugins like AllVideos or similar to easily handle the video content.
In all cases, you will be able to find off-the-shelf Joomla templates that suit easily.
Finally my last comment would be if you don't want to tinker with the code, go Joomla. If you do want to tinker with the code then either is a good choice but I would argue that Joomla's code is easier to learn and develop with than Drupal's.
Hope this helps.
Regards,
Andrew Eddie
Core Joomla Developer
www.theartofjoomla.com