The way doctors deliver bad news has a significant impact on the therapeutic process. In order to facilitate doctor's training, we have developed an embodied conversational agent simulating a patient to train doctors to break bad news. In this article, we present an evaluation of the virtual reality training platform comparing the users' experience depending on the virtual environment displays: a PC desktop, a virtual reality headset, and four wall fully immersive systems. The results of the experience, including both real doctors and naive participants, reveal a significant impact of the environment display on the perception of the user (sense of presence, sense of co-presence, perception of the believability of the virtual patient), showing, moreover, the different perceptions of the participants depending on their level of expertise.