USPSA permits inner/outer belts; many competitors choose to keep holster and pouches attached to the outer belt (semi-permanently), and either the 'stingray' or the 'tec-lock' works okay.
IDPA prohibits use of an outer belt; in IDPA, the paddle attachment is popular.
I find the fixed loop to be preferable. You can special order from Bladetech a custom-made fixed loop holster.