An EQ changes how sound is balanced. Enhanced Headphone Mode changes where sound comes from.

Enhanced Headphone Mode uses a personalized HRTF (Head-Related Transfer Function) created by Immerse. An EQ adjusts sound for your taste or hearing, or to bring out certain parts of the game mix. An HRTF is a spatial profile: it doesn't change the game mix, it places each sound in its correct 3D location.

For example, an EQ might make footsteps louder. An HRTF keeps the footsteps at the same loudness, but lets you hear exactly where they are: to your left, a few steps away, approaching fast.