Preparation for mass casualty incidents (MCIs) is highly important but difficult to accomplish. Incidents are rare, often complex, and training is costly. However, with the development of consumer grade virtual reality (VR) hardware, immersive training simulations have become affordable for competency training. To make simulations effective, users have to be immersed and feel present in the simulation. We have developed a VR training system for MCIs in a user centered design process with emergency personnel and further improved the system to increase immersion and presence. In an evaluation with eighteen paramedic trainees, we compare six hypothesized design improvements between the two simulations, such as using a menu or a simulated emergency bag for interaction. Results indicate clear user preferences of interaction styles related to immersion and presence in MCI VR simulations.