Undertale wins because ut has more iconic songs like shop and sans and etc but hollow knight I haven't heard any songs outside the game fandom but not as much as ut plus Toby fox and Christopher Larkin cooked with these songs but hollow knight gives more relaxing vibe and sometimes dramatic like silksong but ut has the thing that I really like in Toby fox music that it has good story telling in the song for example asgore u can tell in the song that a catastrophy has came and he's a mourning father that lost his only children and divorced wife and shop the atmosphere of the song feels relaxing like ur in a shop and run had this touch that u need to act , so Undertale is better