What is stronger for barbs this season?

Melted Heart of Selig

or

Banished Lords Talisman?

Also why is it better than the other.

Selig + endurant faith charm makes you immortal
You will also cut through all t12 content

only for high pit push you can swap endurant faith charm for banished lord talisman, but you will no longer be immortal
See pit ladder 136 on barb https://helltides.com/pit

So should I use that charm instead of banished lords?

yes, no one uses banished lords outside of pushing pit ladder. Endurant faith gives you immortality

Gotcha. I appreciate it