Modern 1911 practice makes an external hammer just a vestigial downside.
IDK if it's a "downside," but there's certainly very little reason to manually manipulate the hammer on a 1911. About the only reason I can think of is that some folks with weak/arthritic hands find it easier to rack the slide during loading if the hammer spring is taken out of the resistance equation by cocking it. And the beavertail safeties that are beneficial with the modern/superior grip technique of getting high and tight would hinder a condition-2 carry approach.
Now, having a hammer mounted on the frame (whether visible or not) has certain advantages over a slide-mounted striker. But the ability to use the hammer as a manual control... meh.