IMO:

SPC>skunk2>ingalls

But this is because I autocross and would want to make lots of adjustsments to my allignment. You cant beat ingalls for quality/reliability, but its much more of a pita to change your camber settings.

Both the S2 and SPC have adjustabe ball joints, which slide around much like camber plates on a MacPhearson strut car. They're easily accessible and easily adjusted. SPC has a great reputation for quality, but some people have had issues with the S2.

I personally don't have a camber kit yet I do the ghetto allignment h: