Depends on Personality
The text for each of the skills reads as such:
Charisma measures your ability to interact effectively with others. It includes such factors as confidence and eloquence, and it can represent a charming or command personality.
Charisma saves typically depend on the players' personality/presence being interfered with by an outside entity. They are typically used to resist banishment type spells and possession. If you want to flavor it as characters forcing out an encroaching mad personality or the corruption of the character's personality, Charisma saves can be used.
Wisdom reflects how attuned you are to the world around you and represents perceptiveness and intuition
Wisdom saves are often the better save for madness which cause direct effects. By direct effect, I mean it causes the player to take or not take a certain course of action. You'll see it being used when hallucinations occur or when characters are perceiving friends as enemies and vise versa.
Ultimately, it's your choice
It's really down to how you want to flavor the incursion of madness.
A cursed statue may encourage characters to act paranoid, corrupting the personality of characters within range and requiring Charisma saving throws. This can be a really great lead for groups that focus on roleplaying as it can be treated as a character flaw for the duration of the effect. Alternatively, the statue could cause the feeling of being dragged away and requiring Charisma saves to exert their presence on the plane.
For Wisdom saves, the cursed statue may be in an area of corruption which messes with a characters perception of one another, leading to more direct actions such as attacking one another or seeing false terrain.