Lou Fine was the best draftsman of the bunch, which sounds like less of a compliment than I intended. A superb artist, and I love to look at his stuff.
Jack Cole was, perhaps, the most wildly imaginative, and his rubbery characters (I suppose he'd say 'plastic') were like animation on the page.
And Eisner was Eisner—a director, a cinematographer on the page, an all-around inspiration, always finding something new in the interaction of pen on paper.
Link to the book:
The Spirit (1945-04-01) - Chicago Sun