Think of like headphones or fountain pens. There are a lot of different nuances if you want to investigate to search for the perfect keyboard. Switches, plate material, plate mounting style, case material, sound dampening, layout, firmware, et cetera. Some people are very concerned with how the switches feel, or the acoustics, or the perfect layout that is unlikely to be a standard QWERTY layout.

Or you can just try a few switches, pick what you like, pick a size and features, and call it done.