How do PhD admissions committees view double majors? I have read and heard conflicting opinions on this topic, and would like to see what some of you have to say, particularly related to CS.

Does earning two bachelor's degrees as an undergrad, considering all other things equal, provide any advantage over another applicant? That is, saying that this person earning two degrees is still able to participate in quality research throughout their undergraduate degree and is not slave to the curriculum.

Would, say, a MechE/CS student maintain a leg up applying to a CS program related to robotics? A Math/CS applying to theory-based CS? Does it vary between fields?
Would, say, a MechE/CS student maintain a leg up applying to a CS program related to robotics? A Math/CS applying to theory-based CS? Does it vary between fields?


All else being equal, YES.  Speaking specifically for theoretical computer science, I am much more likely to recommend a PhD applicant for admission if they have a strong mathematics background.  A second major is not the more important thing, though; majors are just administrative hurdles.  I look for which advanced math classes the applicant has taken, how the recommendation letters describe their mathematical ability/maturity, and how fluently they use mathematics in their research statement.

Yes, the effect varies significantly between fields.  For example, my robotics colleagues are much more likely to recommend applicants with strong mathematics backgrounds, and my software engineering colleagues are much more likely to recommend applicants with software industry experience.

Of course, as Daniel points out, ceteris is never paribus.