Please explain "built down hull"

While looking around for the "perfect boat" I came across the term "built down hull" in reference to lobster type hulls. No one offered an explanation of this term, and I guess in New England it is common knowledge, but not here in Texas! What does this mean, and what advantage(s) does it have over "conventional" hulls? Thanks.

 

In a "built-down" hull the planking forms the "tuck" in the transition from the hull to the skeg. Internally this forms a well that the shaft runs and allows a short bore-hole through the sternpost. In a "skeg" hull, the planking follows the hull buttock lines in a flowing line to the transom, and the skeg is built up of deadwoods and bolted through the keel. This is easier to build, but requires a long shaft bore-hole.

There are very vocal camps on both sides of the question of which method is best. Please be aware that I grew up in "built-down" country, so I may be biased. The pro - con arguments (assuming traditional plank-on-frame wooden construction) run like this:

a built-down hull is stronger
a built-down hull is more prone to garboard rot
a skeg hull is faster because of less wetted surface
a skeg hull is prone to becoming loose due to working of the keelbolts
a skeg hull is easier to build
a built-down hull is more seaworthy
and on and on and on ....

 

Thanks mmd, more info to chew on.........

 

This is the illustration I tried to load. Built-down is on the left, skeg-built on the right.