Mutt,
yes, you're right that the figures are there for when it's just got to be done. Still wouldn't fancy my chances, though!
The slats/flaps question depends on the construction and operation of the devices. On the 747, the leading edge flaps ('Kruger' flaps) are panels that are hinged at the forward edge, and stow flush to the lower surface of the wing. When deployed, they rotate about the hinge and end up sticking out forward of the wing leading edge. In this position they effectively increase the wing's surface area and camber. This produces more lift (increased CL max) and a higher stalling angle.
Slats, on the other hand, are a method of moving the wing's leading edge forward to both increase the wing's effective area and produce a 'slot' behind the displaced leading edge. This slot is configured to allow air from below the leading edge to flow over the upper surface of the wing, thus 're-energising' the airflow over the top of the wing. This has the same overall effect as the Kruger flap, but can be more effective in increasing the stalling angle. As you say, you see both types on airliners, but as a generalisation Kruger flaps are better for heavy jets trying to obtain the lowest possible speed on approach, while slats tend to be better at providing increased manoeuvrability.
Hope that's not too confusing!
[This message has been edited by scroggs (edited 16 November 2000).]