I think grass is a nice indicator of how an airport is either neglected or run with pride.
Go to any Spanish airport and you will see nice manicured watered lawns around the public approach roads. Now have a close look at Luton. The first view most arriving car passengers see of Luton is the Ibis roundabout with grass that looks like straw and weeds around 3ft long.
On AENA, I'm cautious because of their links to the Spanish government. Do they have the capital to invest in the airport on top of their home market?
Don't forget the 49% that is owned by AXA. They have plenty of money.