Daniel Lemire:

Though I have many brilliant graduate students, I love working with undergraduate students. And I am not at all sure that you should favor people with graduate degrees, given a choice. Many graduate students tend to favor abstraction over practical skills. They often have an idealized view of the world. Moreover, these students are often consumed by research projects, theses, or dissertations, and the publication of scientific articles, which limits their time for concrete actions. On the other hand, undergraduate students, in my experience, show more enthusiasm for concrete and useful projects, even if they are not prestigious at first glance.