What is the purpose of a Dual Degree?
I think you should apply if you find both the degrees interesting, and they are complementary. For example, Physics and Computer Science if you aim at writing very good quality physics models (e.g. climate models). Maybe it is hard for you to say what you really want, and therefore it might be hard to judge whether or what dual master (if any) would work for you. On the short term I would try and see if you are drawn towards both masters. If so, you could get a dual degree. Do mind that I suspect two degrees is more work. If you are up to it, and willing to dedicate the time, it could be worth it. On the other hand, I would not recommend just doing it because you feel it might look good on your resume.