Actually, I have no idea as my experience with Wordpress is new.
One thing ( and I know nothing about CMS's ), how do newcomers like Concrete 5 etc look in terms of competition. It's easy for developers to migrate from one to the other I guess, and there are likely others.
An agency I spoke to today told me they and a few others in the area are happy with Concrete 5 , when I asked why they preferred it to Wordpress. The answer was not specifically one versus the other, just that they used another.
There is no easy answer to your question. They are apples and oranges. For most people it's a matter of preference because all of the top CMSs can be customized to suit your needs. It's just a question of comfort with the interface & coding. Security, of course is important too - as is the support community.