Physically they are identical, have 4 buttons (4 tactile micro-switches).
Typically HAT's in joysticks* are physically 4 buttons - not counting the press button in some HAT.
In "8 way" POV HAT the diagonals (NE, NS, SW, NW) of "8 ways" is created by drivers when 2 near buttons, e.g. N+ E, is pressed simultaneous,
why 8 ways HAT's was never much practical, being a hit and miss.
But in CH gameport gear the HAT's have a physical limitation in plastic guide for avoid press two near buttons (e.g. N+E) simultaneous, due the limitations of gameport drivers.
But is easy modify this "Gameport era" HAT for for work as 8 way if want, and use as POV HAT (8 way) with a modern USB controller, like BU0836A, the modification is explained in this old page (that soon became "extinct") :
http://snomhf.exofire.net/8-WayHat.html* Exception is VirPil and VKB joysticks, these use ALPS 8 way (8 physical buttons) + press button switches in their joysticks, but these require specific support in firmware.
Due this can't install an ALPS 8 way switch for replace a 8 way HAT (that physically is 4 buttons) in common joysticks.