Both mobile apps and responsive-design websites (web apps) can be used to deliver mobile health (mHealth) interventions, but it can be difficult to discern which to use in research. The goal of this paper is to present four case studies from behavioral interventions that developed either a mobile app or a web app for research and present an information table to help researchers determine which mobile option would work best for them. Four behavioral intervention case studies (two developed a mobile app, and two developed a web app) presented include time, cost, and expertise. Considerations for adopting a mobile app or a web app-such as time, cost, access to programmers, data collection, security needs, and intervention components- are presented. Future studies will likely integrate both mobile app and web app modalities. The considerations presented here can help guide researchers on which platforms to choose prior to starting an mHealth intervention.