In terms of technical capability, what are the comparative advantages and disadvantages between the following?
Both DUAT (DTC) and DUATS (CSC) provide the same information. They are functionally equivalent.
You also left one out: Lockheed-Martin operates a web-based briefing service at https://www.1800wxbrief.com/ .
Which you prefer to use for interactive access is largely an aesthetic consideration - as a pilot you can sign up for an account on each of these services, so the usual advice is to sign up for all of them and use the one you like better (personally I used to prefer DTC's DUAT interface, but the direct (1800wxbrief.com) system is a now my preference for web-based briefings when I'm not using ForeFlight).
From a non-interactive standpoint, CSC DUATS has an API that can be used by other programs (like ForeFlight) to receive weather/NOTAMs/etc. and to file flight plans. This can be advantageous, however Lockheed-Martin has recently (2013) implemented an XML-based API that lets application developers directly communicate with the automated flight service system, and it is likely that this will be the preferred way to handle this sort of thing as time goes on.
Technically, there shouldn't be a difference between these providers. Both providers were tested by FAA to confirm that their major functions meet FAA's standards and requirements. Although, each service service has slightly different features and presents the information in different ways. It is more a matter of personal preference and likeliness, and one's comfortableness.
Both these services use FAA database to obtain weather and aeronautical information and to file, amend, and cancel flight plans. They provide direct access to weather information via a National Airspace System Data Interchange Network II (NADIN-II) interface to the Weather Message Switching Center Replacement (WMSCR) System.
In addition the to above mentioned services, many people like FltPlan. It is also approved by FAA. FltPlan is is funded by advertising and provides a better format and information than government subsidized programs.
Aviation Weather Center is another option (Aviation Digital Data Service) which is funded by FAA. It is an excellent source for icing conditions. It does not meet all requirements of FAA.
The bottom line is that whichever service tells you all the information and you are comfortable with it not to miss any critical information is the most suitable for you. However, many people plan their flights in one service and then double check it with others to make sure that they haven't missed anything.