Academic on-site conferences are vital for scholarly exchange and knowledge advancement, yet they contribute significantly to environmental burdens. Considering global sustainability challenges and the limitations of videoconferencing, Social VR offers an immersive alternative that replicates physical conference settings and enables avatar-based interaction. While existing pilot studies have explored perceived benefits and limitations of Social VR, empirical research comparing conference formats with respect to ecological, social, and economic sustainability remains scarce. To address this gap, a mixed-methods study was conducted with participants (N = 32) of an academic conference held in a Social VR environment. Data was collected via questionnaires combining validated scales and open-ended items. Results show that 43.8% of participants preferred on-site conferences, 40.6% preferred Social VR, and only 15.6% favored videoconferencing. Reported advantages of Social VR included ecological and economic benefits with socially favorable interaction conditions. These included a stronger sense of presence, more inclusive participation, and greater comfort in communication than conventional videoconferencing. Overall, the findings indicate that Social VR is a promising intermediate option, combining ecological and economic advantages with socially acceptable interaction quality, while leaving specific gaps in informal networking and nonverbal richness to be addressed by future technological and organizational design.