With the growing interest in hydrogen as a clean energy carrier, understanding underground hydrogen storage subsurface behaviour is crucial for successful implementation. Thereby, reservoir simulations offer critical insights into reservoir characteristics like storage capacity, pressure dynamics, and gas migration routes, making them indispensable for evaluating, enhancing, and monitoring gas storage systems. This study presents a comparative analysis of two distinct reservoir simulation tools, evaluating their results in simulating the injection and storage of hydrogen at the former gas storage site of Ketzin in Germany. Compared are the results of a commercial simulator (CMG GEM) and an open-source option (MUFITS). Results show good agreement between the model results in various parameters such as plume spreading and bottom hole pressure. This study demonstrates the confidence in using an open-source simulator as an alternative to commercial solutions.