Comparing the two fragrances…

Commodity

Monolab
Leather
Slash
Only in Leather
Shared character
Both Leather and Slash share a leather note and feature woody, amber, aromatic, and fresh spicy accords.
How they differ
Leather contains notes of vetiver, cedarwood, ciste labdanum, myrrh, cocoa, styrax, juniper, akigalawood, oregano, pine needles, cement accord, and cade, resulting in smoky, resinous, animalic, balsamic, and warm spicy accords. Slash contains notes of amber, tonka bean, juniper berries, cashmere wood, iris, and agarwood, resulting in powdery, earthy, iris, and violet accords.
Who each suits
Leather suits those who prefer smoky, resinous, and animalic profiles with elements of cacao and wood. Slash suits those who prefer powdery, earthy, and iris-centered profiles.
Only in Slash