well it really depends on many things
If you have allot of windows and light coming through and the bedroom has less light then yes the bedroom is better
Most newer places the living room is open to the kitchen and other parts of hte house, So if you dont mind making a ton of noise that is harder then seal then in a room.
Also in a room that is closed unlike most living rooms you wont need such a big sub to get the same output as in a living room that is open.
Also if you have young kids well the living room is not a place to put expensive equipment.
I am not putting none of my ht stuff in the livingroom in my new place for those exact reasons. Plus a dedicated room is cooler