Accurate urban microclimate modeling is crucial for understanding and mitigating the urban heat island effect and its effects in outdoor thermal comfort. This study compares results from two urban microclimate simulation engines tested in the Georgia Institute of Technology campus: the OpenFOAM-based urbanMicroClimateFoam solver and ENVI-met. UrbanMicroClimateFoam is a fully coupled solver designed to capture complex interactions within urban environments. The simulations are validated using data from on-site weather stations across the campus. By comparing the performance of urbanMicroClimateFoam and ENVI-met, this research evaluates their accuracy, computational efficiency, model complexity, and simulation time. Results show that urbanMicroClimateFoam offers more accurate predictions of outdoor thermal comfort and microclimate patterns for this case study. The study confirms the solver's potential for simulating urban heat islands and informing sustainable urban planning strategies. These findings contribute to optimizing urban climate simulation tools, enhancing decision-making for outdoor thermal comfort, and mitigate the urban heat island effects while promoting more resilient cities.