With the Heart of the Universe, Thanos was easily able to overcome the Living Tribunal.
With the Infinity Gauntlet:
- Thanos was momentarily drained by Quasar
- Thanos was equalled by Maelstrom, in an alternate reality (still part of the Multiverse)
- The Living Tribunal didn't interfere with Thanos because he only sought to replace Eternity - Thanos wasn't a threat to the wider multiverse.
- Thanos was still affected by the powers of Order/Chaos & Love/Hate
- The LT didnt intervene when Nebula obtained the Gauntlet because the Living Tribunal sees the future (as agreed to by Warlock during his trial) and Nebula's eventual defeat.
- Warlock was "challenged" by the Living Tribunal (Would Thanos with the Heart of the Universe be challenged by the LT?)
There are more instances that imply the Gauntlet's inferiority to the Heart.
What proof do we have that the Infinity Gauntlet IS equal to the Heart of the Universe?
Saying that the Infinity Gauntlet is equal to the Heart of the Universe means you're essentially saying that each reality's original 'Infinite Being' is greater than the cosmic judge of all realities.