I get asked this often and feel some outside clarity is required as such I do recommend reading this discussion on LinkedIn. It hold very valuable insight into which platform you should be looking at when choosing a CMS (content management system) for your website.
The argument runs, which is better for SEO (Search Engine Optimisation - the process of getting your website up the rankings in Google). I have often felt Joomla to be lacking in this area and indeed I now have a client who is suffering from this. He cannot get Joomla to do what he wants so he can rank well on Google.
My recommendation therefore is this:
1) Blogger.com - if you are looking for a Blog to bolt onto your website, this is the best solution, easy to update, completely customisable and as I have always said because it is part of Google it most likely gets more attention from Google.
It's cheap and easy.
2) WordPress - it you are looking for a ground up CMS solution for a website that consist mostly of News and Updated content then you cannot go wrong with WordPress - the killer feature is that it is so easy to update for the Admin people. If this part is easy then you have a real chance that people will update their own website. Make the CMS to complicated and marketing departments won't update their own websites.
3) Custom CMS solution - if your website need specific requirements, then you need to go the custom way, we build most of our custom CMS solution from a complete;y search engine friendly angle, we start with the search engines and build everything from there.
You get what you pay for.
4) Other solutions including Joomla and Drupal - they are brilliant but so much more complicated, they work really well if handled by an 'expert', but in the hands of your marketing department, PR agency or whoever you have decided to look after the website - I have to say these complicated options are lacking and therefore not recommended.
I never rule out options, but I firmly think the right tool for the right job, I have yet to come across a website that needs Joomla.
Link: Google Keywords Comparison between Joomla and WordPress.


