CMS suggestions for high traffic

I am in need of some advice. I work for a company who has many online newspapers/magazines. We currently use a licensed CMS that is quite robust. If I were to move some of the sites to a new CMS, what would be a good suggestion (open source or propitiatory)?

I was a freelancer for a long time and have experience (smaller projects/sites) with some of the open source CMS systems but would like to know if there is anything I should consider before making those decisions. I love Joomla and would specifically like to know if that CMS would be able to handle the long-term growth of the site (content, advertising, etc)

Keep in mind, these publications are very respected publications so this is no "let's see how this kind of site would work" sort of thing. Cost is not necessarly a huge issue.

Here are some basic stats for one of the sites (1 month):

Total visits: 183,803
Total page views: 415,615
Total hits: 19,917,538
Total megabytes transferred: 125,538
Average visits per day: 5,937
Average visits per week: 41,562
Average visits per month: 183,803
Average pages viewed per visit: 2
Average pages viewed per day: 13,426

 

Go for Drupal, it has been used by online newspaper/magazine like : The Onion, Popular Science, NY Observer, Fast Company, BBC Focus Magazine, BBC History Magazine etc.

 

Both Drupal and Joomla have many commercial installations. It's not us against them. I've been using Joomla for a very long time and been pretty happy with everything except the user commenting.

This might help http://www.alledia.com/blog/open-questions/open-question-major-companies-using-joomla/

 

I fins joomla easier to look proffesional.

 

Haven't tried Joomla but heard good things about it.

 

I would prefer drupal.
You can achieve this functionality by Views and panels module of drupal.