After trying my car with each individual brace on and off, here are my conclusions:
1) Most important is the lower front. The more points, the stiffer you'll make the car, but the more you impede ground clearance. I have the pierce 4 and I bang it off of shit all the time. Luckily it seems pretty sturdy. If you are doing track work, I would recommend either the 4 or the 6 point, they really change the nature of the car.
2) next most important is stiffening the rear, either with an added sway bar or a torsion bar (I have the TB torsion bar). My car really tends to push with the front brace on, and the torsion bar seems to balance it out and make the rear step out more progressively and keep the car in line.
3) The upper braces (strut tower and trunk) don't seem to make nearly as much difference- the car feels stiffer with them on, but I don't think it really translates to much performance benefit in my experience. Others probably feel differently.
Also, i shoudl mention that I am on stock dampers and mountune springs, with no sway bars besides the TB torsion bar. Putting the car on something more adjustable might let you tune these issues out a different way. For me, it seemed like the bracing and springs was a good $/performance compromise. I might go with coilovers in the future, but for now I'm happy with the way the car handles for my uses (DD/canyon running).