Thanks folks.
Meghan,
I rate Scott's Black as a high 8 and a dead ripe LSU Purple as a solid 6 (9 for the sweetness and sugar rush but the taste is nothing special, for my buds). Note that I said dead ripe. If they are not dead ripe, I do not eat them.
If LSU Scott's Black and LSU Purple color, swell, and are picked at similar points of softness to touch and droopiness, then Scott's Black will always be much better tasting than Purple and definitely much sweeter. According to members much more experience that me, a) juvenile LSU Purple trees should be planted in the ground and b) more mature trees tend to produce significantly better figs than when they were younger. Owners of young trees are always told to 'be patient for a few years'.
I have learned that LSU Purple figs hold amazing well on the tree: they concentrate their sugars like no other tree I have and are almost impervious to splitting. Because of these qualities, you can get fig preserves directly from juvenile trees if you allow them to start the drying process on the tree.