More important is what you are seeking to learn. If you do not care how the code is generated then, by all means use whatever CMS takes your fancy. But if you want to learn the base languages on which the net is built, a CMS will, in my opinion, actually hinder not help. Why? Because the more time you invest in learning how to achieve effects using the CMS, the less willing you will be to break out of the straight-jacket.
Learning a CMS does not make a competent web developer, though I'm sure there are plenty of people earning a living out of providing CMS-based sites. If only their clients knew how their sites were built!