I voted CHA.
How intelligent a warlock is has nothing to do with how the spell powers are accessed. They may have done some research and study on how to get in contact with that power but that's not the same thing as powering the magic through intelligence.
The spells' power comes from the warlock's inner self while the patron is a source of instruction and advice. That's one of the key differences between a warlock and a cleric. Let wizards keep INT as the exception to arcane spellcasting as opposed to CHA as the standard.
How intelligent a warlock is has nothing to do with how the spell powers are accessed. They may have done some research and study on how to get in contact with that power but that's not the same thing as powering the magic through intelligence.
The spells' power comes from the warlock's inner self while the patron is a source of instruction and advice. That's one of the key differences between a warlock and a cleric. Let wizards keep INT as the exception to arcane spellcasting as opposed to CHA as the standard.