the polish ones seem to favour the down-curved spike, some almost hook-like. which might be a useful additional function. most seem to be fairly utilitarian & had wood hafts. the hooks were used to drag an opponent off their horse by hooking their clothing or straps, mail, etc.
light horsemans war hammers (nadziak) were popular in poland's nobility long after they fell out of favour elsewhere.
ref:
http://polisharms.com/warhammers/
mine: 15cm across, 2.5 cm. eye hole.