While shopping for a new home this year, I walked through a number of models that had a "media room" setup with a screen on one of the longer walls and a row or two of seats the wide way. (One room had 8 seats across) At first I thought it was odd they set things up this way, but after sitting in one for a while, it kinda grew on me.
What I realized is that this setup is an awful waste of space on either side of the screen unless you can make good use of it.
It also depends a lot on your layout. If you have a door entering the middle of the short wall and windows along the opposite, then you might not want to go to the trouble of moving the door and hiding the windows.
So, as with all advice, it just depends. Post a layout and you can usually get some useful suggestions here.