Stayed at Renaissance-Fira & Cotton House - this year for a wedding in early July. Marriott Gold Status
1. Renaissance-Fira is a very nice hotel and great breakfast. Location is FAR from city center. In a "business park" type area, safe but nothing around. The hotel is trendy and has exterior corridors kinda. My wife loved the room though and the rooms were large. We got pretty much the top floor and the views are awesome. We stayed here because flight came in late and no reason to spend 3X the money on Cotton House, also pretty close to airport. Free breakfast was very solid and fresh. If you dont mind commuting into the city, this place is a great value.
2. Cotton House my wife loved. We are huge autograph coll. people. She took a girls trip to BCN and got upgraded to an amazing room back in January, but this trip our room was very small and interior view. Yes, the hotel is nice and we were at the pool all day, but the room size if you don't get upgraded is euro small. Super nice hotel and trendy. We ate some bites at the pool and had some drinks. All good. In city center and close to everything. On a nice street.

(Last thing, the W Barcelona has gone down in our opinion) room was dirty and loud obnoxious people out front all hours.