Can it just be assumed these are the same thing, or would you define them as clearly distinct things?
I think at the least they're close enough that if you were say, making a game and "Willpower" was one of the core attributes, it could include both, the same way that "Dexterity" in D&D is both manual dexterity AND nimbleness of body despite those not being mutually inclusive traits.
It seems to me that Willpower is, at its core, the resolve to protect your individuality and independence of action from outside influence, and the ability to exert your will like a sort of pressure. A strong personality or will seems to carry weight in social interaction, even if the person does not actively act domineering towards others or have substantial charisma.
Oops double post.
also I was going to say something important but that text preview thing weasyl does, i think I tried to TYPE IN THAT and the bowser blitzed out and here I am with a double post from a previous page.
Okay so, there was this thing from a trip a while ago. This is not the whole section.
Mind Control
Failing a Will Save
A wizard fails a will stave off influence from a mage changing the Will. Or the mind.
I imagine the person expereinces this as
something like OCD
Some effect they must mitigate before anything else can be done
To fail is to never
let it go
The attack comes in
The attack is fought
It will pass though the body
if not resisted
Link
Lone Companion
In a game I suppose you could combine them. I don't know outside that context what subtle differences they might have. I don't use the term "strength of personality" to have thought about it. I do think about The Will a lot, but I am still vague on that concept relative to some of the others I think about, though it is extremely important to me. The time has not yet come to focus on it. I think about it when it comes up, I think about it directly sometimes. But the time has not yet come to really know about it. Even though it is a major part of my system.