It's very important that, not only the system you are willing to use is important, but also the transfer to this system. How much URLs we are talking about? 1000, 10000 - 1.000.000 ?

Wordpress might get heavy and might need a special setup for high volume content sites, or high traffic sites. Changing the system is a huge risk that should be evaluated before doing the change. Remember to keep track of each single URL and redirect accordingly to the new URLs with a 301 in case the URLs really HAVE to change.