3rd party cms solutions like drupal, etc are really very good but invariably website designers company gets involved for the basic setup etc. they are said to be flexible to take care of your future works but we are not sure if after doing basic setup the development company's support will not be required. We haven't used much of such 3rd party solutions. We have experience with kentico, sitefinity, etc but the independancy from the developer firm (as quoted by the CMS solutions) are not found to be of much ado. It is basically that if all of requirements are met by some particular cms system (well and good) otherwise one have to contact development firms to customize it.
Modification/addition of features not available
Our CMS website design offers most of management features and if some thing is lacked it can be worked around easily... so once it is on a website, it will work pretty well with the functionalities.
Features of course can be added as per requirement and demand and being our own CMS which will be easy to work with to provide efficient integration. In 3rd party solutions developer never get the core of the management systems and have to provide work around solutions... in some case which was not feasible
