Marta&Paul’s place is indeed enjoyable, extremely close to Sagrada Familia and also well connected to the metro network. The hosts were friendly from the moment we booked and answered all our questions and offered solutions for our requests (we had a late return flight and needed to store the bags, since the apartment was booked, they adviced us where to safely store them).
The neighborhood is safe, we had no issues with the noise (unless you sleep in the living room, where you have the usual street noise) and there are some small supermarkets around.