While both omnisexuality and pansexuality fall under the multisexual / m-spec umbrella (attraction to multiple genders), the psychological distinction centers on gender salience.
Pansexual individuals often describe their attraction as 'gender-blind'—meaning gender presentation does not significantly influence their attraction. In contrast, omnisexual individuals recognize and experience attraction to all genders, but gender often remains a meaningful factor in how attraction manifests.