Depends on the size of the room. You should look up the right size for your room. Also, depending on the type of content you watch, you have to sit a certain distance from the tv to see the difference between resolutions.
so you’d have to sit closer to a 55 vs 65 to see the difference in resolution. The higher the resolution and the closer you have to sit and or the bigger the tv you need to see the difference at certain distances.
I sold my 55 inch and bought a newer 65 inch and I love it. But 55 was a great bang for the buck at the time, just had to sit somewhat closer to it to really appreciate the 4K content.