The Arts is a dated, 80's-style highrise smack in the middle of the tourist traps and near the beaches for which Barcelona is not famous. It's expensive, and opulent in the way that a coke dealer's living room might be opulent. It is not near anything that could remotely be called culture, unless you count sidewalk restaurants with pictures on the menu hawking sangria and frozen paella.

Barcelona has lots of wonderful hotels. La Florida is not near the Gaudí stuff but is near a beautiful, historic and upscale neighborhood. It is vastly better than the Arts, IMO. The new W will also be open by the time the OP is here (I think) though it is also out of the way, in the Diagonal Mar area. The Claris is also quite nice, though is in need of a touch-up, but very central. There are also a lot of good four-star properties like the FTer-favorite Calderon.

FYI, Plaza Cataluña (and the Best Western Regina...snicker) are both not only in the area of the Ramblas, they are actually on it.