Help with Social Networking Portal

[paganwinter]

Hi, I am building a Social Networking portal and would like to know certain things before going ahead.
I know a lot of platforms, CMSs and Engines are freely available that can be customized.
But what I'd like to know is which of these is better suited for a Social networking portal which would also have Gaming elements in it? The following are the things that I have tried out:

CMS:
Joomla
Drupal

Social Networking Engines:
Elgg
PHPIzabi

PHP Frameworks:
CakePHP
CodeIgniter
Symphony
Zend

Of these, which would be best for ease of use, ease in customizing, Scalability, Security, Robustness?
Is it a good practice to use readily available engines or is it better to learn from those and try to build one your own using any of the PHP Frameworks?

Thanks in anticipation...

[blackhorse]

What is your decision?

Could you share it with me? I am searching for the solutions for the same purpose.

In this case

Using Framework like CodeIgniter, I would have more power and freedom, but learning curve and developing time will be longer and more too.

Using Social Networking Engines, makes more sense, if these OSS fit well with my project. These are for the special purposes of social networking, it should fit well.

Using CMS like Drupal, the developing time will be between the above two approaches.

I would choose Social Networking OSS from

Elgg
dophin
PHPIzabi

Any one has experience would like to give some advices, in the above 3 social network community OSS, which one you will recommend?

Thanks!