The bars that are installed now are not the same strength as they used to be. Many are hollow. The advantage of bars is that in hot weather the windows can be left open without security risk. We had most of the bars removed in main areas as I hated them. We had the re-enforced Clima glass and alarms. We had them in the kitchen and basement and was useful for the cats as they could come and go.
Never been burgled in 15 years in Spain although we always had a dog. Our neighbour, a spanish Lawyer was burgled, they even took the car keys and drove off in his lexus! The robbers were caught eventually, was a security guard on a nearby building site. Worst areas are eg. Calahonda where there are a lot of short term tourist rentals, mainly druggies who just want cash. Someone we knew had a villa overlooking Los naranjos golf course, he was murdered by a drug crazed spaniard for 1000 pesetas…not just the Romanians, spanis prisons are full of er….spanish citizens.
I have to say I never felt worried or threatened about crime in Spain.