@Petermau: It would be nice if you would just try to answer the question instead of questioning why I need to ask a question. If I ask it, then it means I must have a reason. Please don’t use this as a medium through which to attack my decision to ask a question.
Regarding your question, on the other hand, I’d like to use them as ruler measurements, not font measurements; nor did I ever mention anything about font sizes. The nature of these other units as absolute units is exactly the problem: because they are absolute, they are not consistent with certain elements other than font; pixels though are relative units, and thus anything a distance of 5px will be 5px and a proportional distance across any user’s screen (since it is relative to screen resolution, not absolute physical lengths), while 2 cm may easily be any distance depending on the screen size/type/etc.
Therefore, pixels are superior units for my needs, which are measuring column & row widths in spreadsheets. You could even test this out on your own, if you want: x points for column width is not the same as x points for row height; on the other hand, x pixels is exactly the same on both the column width and row height. To reiterate, it’s exactly the non-absolute, but relative, nature of the pixel unit that benefits me; to use anything else is frankly a pain.
I do appreciate both of your responding. Thank you.