Chance to trigger lvl 1 Blood rage vs self cast blood rage

I have an item that says "15% chance to trigger lvl 1 blood rage when you kill an enemy."

I am also running Blood rage as a gem.

Which one would take priority here?

I've been testing it myself but i have to many buffs that trigger on kills to get an accurate read on my DPS to see which one takes priority.

New instance of Blood Rage overrides an older one, regardless of effect/level. Because otherwise it wouldn't be able to refresh the duration. It is a special buff for that matter.