65" all day long.
I was redoing my den, and put a TV over the fireplace. It was between a 55" or 65" Frame by Samsung, and after making cardboard cutouts to show size, my wife insisted on the 55". She said, "You have a 75" Mitsubishi DiamondVision in your Man Cave, 55" is fine for the Den."
2 years later and I'm still bitter. The 65" would have been perfect, and a 70" would even work. When tv shows do a cut scene showing someone's phone with a text message, I have to pause the TV, get up, and walk in front of the screen to read the damn writing! Not with my 75" TV. Get the 65" and thank me later.