It's Not Rocket Science
Implementing content management on a small to medium scale can be as simple or as complex as you want it to be. Do you need a content management system? The best way to find out is first to understand your content management requirements and then compare this to what each of these products provide out of the box. If buying a CMS gets you 70% of the way down your requirements list and only costs 40% of what it would take to develop yourself, go for it. If your needs are small, however, consider building an in-house solution on top of readily available (and in some cases free) software (for instance, MySQL and JBoss or PHP). You could save yourself a lot of money and grief.