Bellver/Aguilar should be the more stable pair in long exchanges, with Bellver likely anchoring the left side and dictating pace through the middle. Santamaria/Alvarez can hurt them if they speed the match up with early net pressure and aggressive bandejas/víboras, but that carries higher error risk indoors. In Gijón’s typically quick indoor conditions, I lean Bellver/Aguilar in a tight match if they control the center and lob well.