Large high-resolution displays have been shown to improve user performance over standard displays on many large-scale visualization tasks. But what is the reason for the improvement? The two most cited reasons for the advantage are (1) the wider field of view that exploits peripheral vision to provide context, and (2) the opportunity for physical navigation (e.g. head turning, walking, etc.) to visually access information. Which of these two factors is the key to advantage? Or, do they both work together to produce a combined advantage? This paper reports on an experiment that separates peripheral vision and physical navigation as independent variables. Results indicate that, for most of the tasks tested, increased physical navigation opportunity is more critical to improving performance than increased field of view. Some evidence indicates a valuable combined role.