Due to the internationalization of higher education and the widespread use of English as an academic lingua franca, universities are increasingly choosing to introduce English-medium instruction (EMI) programs. However, EMI programs are neither monolithic nor English-only in their implementation. Although research has acknowledged the variation with which EMI is implemented across contexts, little is known about students' motivations for choosing monolingual and bilingual EMI programs or how students' beliefs about these programs compare. This study attempts to address this gap by examining students' motivations and beliefs about the academic and professional benefits and challenges of studying in monolingual (full) and bilingual (partial) EMI engineering programs in Turkey. A questionnaire was administered to 198 undergraduate students, and the responses of students in full and partial EMI programs were compared. The results revealed significant differences between groups with respect to motivations for EMI study, with students on full EMI programs more optimistic about the professional benefits of EMI compared to students on partial EMI programs. Differences were also found regarding students' self-reported English proficiency and beliefs about the academic benefits of EMI programs. The findings are discussed in line with EMI policy and language support.