Strange non fluid hesitant connection between "c" and "h" on the Mitchell. Look at Steve's. A lot of this looks to be a single hand. Some single pen...
There has always been a lovely flow to Joni’s signature, which is missing in the OP’s example. Even on things like this lithograph, which is, on the face of it, scruffier than mine, there’s a swift fluidity in the movement of her strokes: