You touch it more than anything else on the desk, so small differences add up over a working day. Start with layout and connection, then switches, then everything else.
Layout
- Full size has a number pad. Useful for spreadsheets and data entry; it pushes the mouse further out.
- Tenkeyless (TKL, about 87 keys) drops the number pad and keeps arrows and the function row. The safe default.
- 75% keeps arrows and function keys in a tighter block. Popular with developers who want everything without the width.
- 60% / 65% drop the function row (and arrows on 60%), reaching them through a layer key. Great for desk space; expect a week of adjustment.
Switches
- Linear (smooth, no bump), tactile (a bump at the actuation point) and clicky (a bump and a click). Clicky switches are loud on calls and in shared rooms.
- Low-profile switches feel closer to a laptop. Scissor keys, as on most office keyboards, are quieter still.
- Hall-effect / magnetic and analog optical switches let you set the actuation depth and add "rapid trigger". Mostly a gaming feature; harmless for typing.
- Topre (electrostatic capacitive) is its own feel: a rounded, cushioned bump. Loved by some typists, expensive.
Other things worth checking
- Hot-swap sockets let you change switches without soldering, so a bad guess about switches is cheap to fix.
- Connection: wired is simplest; 2.4 GHz dongles have lower latency than Bluetooth; multi-device Bluetooth helps if you switch between laptop and desktop.
- Remapping: QMK/VIA support means you can move keys in firmware, so the layout follows the keyboard to any computer.
- Mac or Windows: look for a keyboard with both legends or a hardware toggle.
- Keycaps: PBT plastic wears better than ABS, which goes shiny.
If you can, try a switch tester first. It costs less than one wrong keyboard.