The underrepresentation of female students in university physics courses is a long-studied issue in many countries. Public data from the US, UK and NL indicate that when physics and astronomy are both offered at a university, astronomy tends to enrol up to 50% more female students. Many previous studies show strong gendered motivation differences for physics students, yet comparable studies for astronomy students are sparse. To explore this enrolment trend, we conducted a pilot comparative study exploring how and why astronomy and physics students at a large Dutch university chose their study programs. Identifying and understanding motivational factors, and if/how these may differ per study program, gender, and other variables of interest can help inform future efforts to improve equity.