Removeable (detachable). I test different keyboards and rotate among the boards in my collection. I keep several cables connected to a hub with the loose ends behind a KM switch on my desk.
Among my favorite keyboards are two RF 87ub (55g and 45g), which do not have detachable cables. I am considering modding them to install case-mounted micro-USB connectors.
My first refurbishing project was an IBM XT keyboard, and I installed a USB-B case-mounted receptacle so that I could have a detachable cable. I also have IBM SSKs that came with detachable SDL to PS/2 cables, which I replaced with SDL to USB cables.
A potential problem with keyboards having receptacles for detachable cables, especially mini-USB, is that with repeated use, the connector itself can break or its internal connections can break. Supposedly the lifetime of micro-USB connectors is longer than that of mini-USB connectors, and providing an internal strain-relief cable can help prevent breakage of internal connections.