Gimme Shelter, as it's a better song, though they both conjur up nightmares to be honest. I can never hear 'Helter Skelter' without imagining the Charlie Manson 'family' slicing and dicing poor Sharon Tate and her friends, but then I can never hear 'Gimme Shelter' without remembering all that carnage at the 1969 Altamont Festival which they caught on the 'Gimme Shelter' documentary. The summer of 1969 was just about the lowest and blackest of all possible low points for rock 'n roll.