All CRYPTO-BOX units for USB port (SC, XS and Versa models, inlcuding the corresponding models with USB-C plug) are compatible and use the same API functions. Therefore software which was written for the CRYPTO-BOX Versa will also work with the XS and SC.
The XS (as well as the SC) additionally provides network licensing (read more), and the CRYPTO-BOX SC supports RSA encryption in hardware and allows to set multiple key slots for hardware based AES and RSA encryption. A comparison table can be found here.