The first difference I noted, on the very first hour as we sat in an outdoor table for lunch with our Airbnb host, was the dogs.
We had seen the typical number of dogs in Portugal (no street dogs, however) and without exception they were pulling their owners down the street or lunging excitedly at other dogs. The few times I approached them I was jumped on, slobbered on, or both. We never saw a dog off leash. And they were all so off putting that I failed to photograph any of them!
Barcelona dogs, we saw almost all mixed breed except for a notable number of dachshunds, are muy educados, very well behaved. Some pulled or barked at passing dogs, particularly when a dog was guarding his or her building by watching passers-by from a tiny balcony. But all–I think I noted maybe 2 exceptions–trot alongside their owners or sit politely behind while the owner is in conversation. We saw many dogs off leash, both walking alongside or directly behind their people or waiting silently, staring into a shop in order to keep track of their people. A young man crosses a small plaza, a dachshund scampering around, and as soon as the man stops at the curb the dog runs over, responds to a hand signal to wait, and then trots across at his heel.
Big dogs, huge dogs, little mixed breeds or chihuahuas, basically the same assortment in the states, all well behaved. From time to time we heard an owner correct the dog in a warning tone. No lunging, no pulling. Dogs were on trains (including the high speed train to Sevilla on which I am sitting), dogs sitting in outdoor cafes, dogs wearing the Spanish flag in the parade, even a dog gazing at the Roman columns. Los perros de Barcelona son muy educados.