Many major industries rely on government subsidies to remain competitive and provide the lowest possible price for a commodity. Seeing as these businesses already pay tremendously in taxes it would only seem fair that the government gives back to these companies so they can provide a affordable service for the people of the EU.
No, subsidies within the EU are not beneficial, because they only encourage inefficiencies among the weaker countries. Countries should be rewarded for being high-performing, not for being weak. Allowing subsidies only make sure that the weaker countries hurt the economies of the stronger countries. It is better to reward strong economies, rather than punish good ones.