having owned both: would recommend either!

basilisk: +cable feels more robust +smooth button actuation & shorter travel (excepting dpi key) *rubberized areas are more soft / grippy *has rgb if youre into that (though id prefer to save whatever cost and mass it adds personally) -softer body material (scratches / wears relatively easily) -software feels bloated

g502x: +cable is much finer and very flexible ++2 extra buttons! (or 1 if you count the underside switch) +being ~17g lighter made more difference than i expected +dpi switch feels great + is comfortable to press from a greater variety of angles *sharply clicky buttons, tons of feedback -enough travel distance on the hyperscrtoll switch that i thought there might be an optical switch getting triggered on the way down to add an extra button—missed opportunity tbh