I woud think a CLAD or CLD would open more doors for you in terms of jobs. In my opinion a CTD is similar to a CLAD and not a CLD. Only because it is multiple choice.
I think as companies start to realize more and more that it is a waste of energy, time, money and resources to create their own ATE (Automated Test Executive) in LabVIEW and that an off the shelf solution (TestStand) is a much more efficient, feasible way to go then you will see the market for TestStand engineers pick up.
However, I think it takes a lot more to know LabVIEW because you have to understand Computer Science. With TestStand there are some algorithmic decisions to be made but it is generally a straight forward sequencer. Usually all of the hard code is done in an external language such as C# or LabVIEW. That's why I feel it is more valuable to know LabVIEW.
Also, it depends on what you want out of your career. For example I love doing framework development. Therefore a CTD or CTA are really good options for me.
The nice thing about NI certifications is that it levels the playing field. If an applicant has a certification on their resume then I know at least they have a certain level of knowledge. This way I don't have to guess whether or not they might have a certain skill. Because if they passed the test then chances are they have that skill.
Hopefully this help some. It is my opinion so take it for what it's worth.
