I can speak for wordpress because I never used it, but Joomla! is certainly a product I recommend. I have tried a few different CMS over the years and Joomla! is my prefered option so far.
It's fairly simple to learn, especially since you have used other CMS programs. The idea is to clearly define how you'll manage your content, by setting up the appropriate categories and sections. If you're going to use it as is, you won't have any problems. There's also a great user community and tons of add ons available. It isn't SEO ready but you can use compenents that will make SEO compatible. Actually, I haven't check the Joomla updates in a while so it is posisble that they do have an SEO version out now. I'm not sure. Either way, it can be done.
Now, that doesn't mean it can't be a bitch! If you get into heavy customization, like making your own templates, modifying PHP functions and so on, that's going to require so good old fashion notepad mad skillz! Well... that's the hardcore way of doing it anyway
All that to say that it is highly flexible and customizable able, but it doesn't *have* to be if you're happy with an out of the box solution.
wordpress vs joomla?
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