My principles with regards to the size of a TV...
- Bigger screens are for more people to watch at the same time.
- An individual's experience is about viewing angle (think Occulus Rift)
- There's a narrow range of "optimal" viewing distances.
- It's inversely proportional to the size of the buyers' willy!
Lots of people = Big TV :: Big Room = Big TV. :: Small willy.... you get the picture
Beyond that I refer you to the chart below...