Unsurprisingly, FC Barcelona and Athletic Bilbao want to play the 2015 Copa del Rey Final in Real Madrid's stadium. This was also a recurrent topic when both teams met in the Final three years ago. That time, Real Madrid publicly stated that they had some scheduled maintenance at the stadium and the game was played at the Vicente Calderón instead.
Both parties have a point here. On one hand, the Bernabéu is Real Madrid's own stadium and nobody else's. It should all come down to Real's decision. Years ago, they had to repair the Bernabéu's restrooms right after a Copa del Rey Final between FC Barcelona and Betis, and that's why Real Madrid have every right to reject Barcelona and Bilbao's proposal.
Meanwhile, Barcelona and Bilbao want the biggest stadium available. Considering that the Camp Nou is ruled out for obvious reasons, the Bernabéu is the one with the biggest capacity left. But surely, that's not Barcelona's only reason to ask for the Bernabéu, right?