Aria has a more diverse range of dining options from relatively cheap to high end. It's much quieter without the crowds of tourists that can fill up Bellagio's public areas. The one issue is that MGM hasn't done a full refresh of the rooms at Aria recently, so even a couple years ago the rooms that once felt amazing now feel kind of worn. Bellagio's rooms are largely fresh and new. Getting between Aria and Bellagio is far easier than some people say. Go out the North Valet entrance, take a short walk to Vdara and out the back of Vdara. There is a walkway that takes you to the Spa Tower of Bellagio next to the tram station and it's a short, indoor walk to the conservatory and lobby past the pool area. There is no reason to walk through Crystals, onto the strip and back into Bellagio unless you want to.