That's why they have centimeters (cm). When I buy a TV in Europe the diagonal size is expressed in cm.
People here have a better feeling of what 138cm is than they do for 55' because they are just more used to it.
Neither is a better measurement, it's just a matter of what you're accustomed to. If you were used to banana scale you'd think 8b is easier to understand than 55'.
Yeah, I get them mixed up all the time. I don't use them.