Design space exploration refers to the systematic activity of discovery and evaluation of the elements in the design space in order to identify optimal solution by reducing the design space toward an area of performance. Designers sample thousand design points iteratively, explore the design space, gain knowledge about the problem and make design decision. According to the literature, Design Space Exploration results in a decision of quality called informed decision which is supported by information visualization. Indeed, the representation of design points is seen as primordial to gain understanding of the problem and make an informed decision. Thereby, in our work, we try to identify which graph is the most suited to the discovery phase and allows designers to make an informed decision. We designed a web platform with four design problem and carried out an experiment with 42 participants. It results one graph more suited to make a decision of quality and to gain the most understanding: the Scatter Plot Matrix.