Large-scale simulations are well-established in medical education for developing clinical decision-making skills and confidence in complex scenarios. However, they require significant resources and time. Micro simulations (Mini-SIMs) offer a cost-effective, repeatable alternative that is easier to integrate into curricula [1]. This study compares Mini-SIMs and traditional simulations to assess their value in undergraduate medical education. Five sessions were conducted with Year 5 medical students, each covering different clinical topics. Each session included both a large-scale simulation and mini-SIMs, with topics assigned at random. The groups remained consistent, and the sessions were facilitated by the same instructor with technical support. Post-session surveys measured perceptions of scenario realism, technical skills, decision-making, and clinical competence using a 5-point Likert scale (n = 33). Students were unaware of the study's aim and were told only that the sessions were part of revision to reduce bias. All students agreed or strongly agreed that both simulation types felt realistic. The development of technical skills was perceived as higher in large-scale simulations (83%) than in mini-SIMs (69%). Improved decision-making was reported by all students after large-scale simulations, while 88% noted similar improvements after mini-SIMs. Clinical competence was rated as improved by 100% of students following large-scale simulations and by 88% after mini-SIMs. Mean performance scores were 77 for large-scale simulations and 70.5 for mini-SIMs. Large-scale simulations remain the gold standard for technical skills and clinical decision-making, while Mini-SIMs offer a resource-efficient alternative with high ratings for realism, learning, and satisfaction. Their flexibility makes them a valuable addition to undergraduate medical education, particularly where resources are limited. Further research should evaluate their long-term educational impact.