I could care lee about all this other stuff. As long as there are two hoops, a floor, and a place for me to sit (or stand) to watch a game I am happy. People put too much into what a building looks like. I spend most of my time watching the game.
The XL Center is competing with the couch, cheap (and better) food, and the 50 inch LED. They are also targeting the big dollar spending patrons. When entertainment can attract the big spender, Marquee acts find the venue more attractive. In turn, Management can charge the higher quality acts higher rent and increase the value for the time spent at the arena.
At the risk of bas-d-izing Ollie's comments, The goal is not for the arena to chase tenants. The goal is to make the facility so attractive that they have to turn away the lower level acts because the schedule is booked with marquee, high paying rents and patrons to consume them.