As far as LCAs go for stock-style springs, I'd recommend the Griggs Racing LCAs
Non-Adjustable Perch:
http://www.griggsracing.com/product_info.php?cPath=4332_4310_4348_4322_2055_3810&products_id=76
Adjustable Perch:
http://www.griggsracing.com/product_info.php?cPath=4332_4310_4348_4322_2055_3810&products_id=72
My reasoning is this - Griggs uses a square style control arm, whereas most other brands use a round control arm. Round tubing can withstand more force when loaded end-to-end, but will be weaker when handling side loads compared to a piece of rectangular tubing, of the same alloy and thickness. This is the same reason that our frame rails are rectangular, rather than round. It just handles side loads better.
For a coilover application, a round control arm is the better choice because the force is being applied to the
ends of the control arm only.
However, in an application with a stock-style spring, a large amount of the force is being applied along the
top of the control arm, near the center. A rectangular control arm is going to give you more rigidity for side loads than a round arm. The spring perches are subjected to tremendous loads (after all, they hold most of the weight of the car), so a round tube being loaded from the side (spring perch) would have to be over-engineered (and subsequently heavier) to be able to withstand the same amount of force applied to it, relative to a control arm that uses round tubing.
Strength in bending and buckling comes from the moment of inertia (I)
I (round) = .12 in^4
I (square) = .21 in^4
Therefore, square tube is about 70% stronger when subjected to side loads. When it comes to cars, this means it can be lighter, since you can get more strength out of less material.
TL;DR:
IMHO for coilover application: round tube, and for stock spring application: rectangular tube
