Despite the influx of research examining various aspects of mobile-assisted language learning (MALL) applications (apps) over the past two decades, there have been no head-to-head studies that have investigated the comparative effectiveness of different mobile apps. The current study addresses this gap by directly comparing two of the most well-researched and popular MALL apps: Babbel and Duolingo. In this mixed methods study, adult learners (N = 59) engaged in studying Turkish as a foreign language using either Babbel (n = 27) or Duolingo (n = 32) for eight weeks. Participants then completed two exit assessments, including (1) a posttest gauging their development of various language skills (i.e. reading, writing, speaking, listening, vocabulary, and grammatical competence), and (2) a survey assessing their user experience (e.g. enjoyment, motivation, beliefs about effectiveness). The results of this study showed that although both the Babbel and Duolingo groups made progress, there were no statistically significant differences between their L2 learning gains. However, for the Babbel group, there was a stronger correlation between participants' study time and their posttest scores. Finally, Babbel users also felt the app was more effective for learning grammar, speaking/pronunciation skills, and for learning about the target language culture. This study discusses the implications of these findings for researchers and MALL users more broadly.