Two networks instead of one
Your eSIM runs on both Orange and Movistar, and the handset moves between them without you choosing. That matters more in Spain than it does in most places. The country spreads its traffic across a long coastline, a high plateau and a lot of distance between cities, so where one operator thins out the other usually holds. You get the better of the two signals at any given moment rather than whichever one you happened to buy.

