Hi there,
If you're seeking for the unique and local Barcelona feeling I would highly recommend to stay in Gracia. But to be fair, there is a huge bias from my side. Whenever I travel to Barcelona I stay around that place.
If you're lucky to stay with Franziska and Pablo I would strongly suggest you to go for it!
Their flat is very well located, close to the metro station Joanic (L4). The historic part of Gracia is in 5 min walking distance.
You'll find dozens of restaurants, small shops, some off-licences etc... .
Coming to the flat. It's a two bedroom with a lounge, kitchen, storage, one extra toilet and bathroom. It's perfect for 4 people, as you will sleep in proper beds.
You will sleep brilliantly as the flat is located on a very quite street.
The flat is sun flooded all day, being located on the 4th floor of an period building. If you're scared of climbing stairs, a small lift will take you up to the flat...
From the south facing balkony you enjoy a superb view over the town! This was my favourite spot.
The pictures are accurate and give you a very good impression about the flat.
Moreover, the flat is well equipped: dish washer, washing machine, fridge freezer, just to mention a few.
We didn't meet Franziska/Pablo in person, but a good friend of them. He gave us a very warm welcome. Communication prior was super easy. He speaks English and French fluently...
Have a good time in Barcelona,
Fred