It really depends on how confirtable you are with both. There is nothing you can not do with either. I however find Wordpress a better choice based on personal knowledge and the ease I have to manipulate it to do what I want but I have used Joomla for years and wouldnt say its any less good.
Both really can do what he asked Unless there are limitations on his part in terms of knowledge that we need to consider. Or if he wants us to compare security issues for him which again both will have a pro and a con.
It all depends on personal preferences.
Have you tried both?
Personally I prefer WordPress more but it is all up to you.
Take a look at the pros and cons of WordPress and Joomla and then pick the one you're most comfortable with
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