What's the difference between square and hex ferrule crimps?

Square (or trapezoidal) crimps produce a flat-sided result that mates well with screw and cage-clamp terminals common in PLC and control-panel work. Hex crimps produce a six-sided result preferred for round screw terminals and many European-style connectors. Threads on r/PLC and r/AskElectronics note that both are acceptable when paired with the correct terminal style, hex is more universal, square is preferred where panel terminals are designed for it.