We replaced our tube TV, gosh, 2 or 3 years ago at least, and I did calculations based on the idea that the screen should at least cover the old screen, with extra width of course. I think a rule of thumb is that you should go a step above that. It’s a new TV! Live a little! Plus, the larger screens do not represent the technological “stretch” that large CRT screens did. Also plus, when we bought ours the sales rep said that the most common buyer’s remorse was that they should have gotten a bigger one. Well, he might say that, but I believed him, so we went with the top end of what we had in mind. I couldn’t even tell you the inches right now. It’s a modest size in the range of what’s on the market ( which offers much bigger ones than a few years ago, ) but it seems very luxurious to us, even now.
Bottom line - get one with a bigger image than the old TV you’re replacing.
If I were to get a tv, I’d want it as big, but comfortable as I could myself. I tend to like my tv to be like a movie screen, where the width is almost as wide as my viewing abilty.
The price difference between most sizes is only a couple hundred dollars these days anyway.