I just recently booked a room at the Bellagio but I'm thinking of changing it to Aria, Vdara or Caesars?

You know that Mirage, Aria, and Vdara are also managed by MGM don't you? For the price you're paying, if you're having 2nd thoughts about Bellagio, then I'd suggest Venetian or Wynn. I've stayed at Aria within the last 6 months and it's nice, but Bellagio is nicer. And Bellagio is also nicer than the Mirage. I've not stayed at Vdara yet, but it's probably close to Aria in terms of quality.