Public opinion has been identified as one of the main drivers of political action in support of sustainable-transport transitions, making it essential to understand when aiming for effective transport policy. Drawing from both quantitative and qualitative data from the 2021 Montréal Mobility Survey, this paper analyzes public perceptions towards two transport projects—a light-rail transit (LRT) and a bus-rapid transit (BRT). Quantitative statements pertaining to five project impacts were compared between the two projects. Both projects had high levels of agreement (between 67% and 80%) regarding expected regional and environmental impacts, but agreement levels were lower for expected neighborhood, cultural, and residential displacement impacts (between 49% and 30%). To contextualize the quantitative findings, qualitative data were pulled from open-ended questions for both projects and analyzed using an applied-thematic-analysis approach. The qualitative responses focused primarily on negative perceptions, providing insight into potential factors contributing to the erosion of social acceptability. Our analysis of open-ended questions underscored contrasting perceptions between the two projects in terms of improvements in accessibility to destinations (minimal for the BRT vs noticeable for the LRT), governance (transparent for the BRT vs opaque for the LRT), consultation processes (adequate for the BRT vs insufficient for the LRT), and construction impacts (lengthy and disruptive for the BRT vs rapid for the LRT). These contrasting quantitative and qualitative results highlight the need for mixed methods when assessing public perceptions. Findings from this paper can be of benefit to practitioners and policy makers as they aim to ramp up efforts to expand public-transit systems.