Another thing to consider between the 1LE kit and aftermarket is if you have the 1LE kit installed at your dealer then you will retain full vehicle warranty. For some people that is piece of mind. Any aftermarket suspension could void parts of your drivetrain warranty (half shafts due to drive angles) and possibly other issues that GM could claim were caused by the aftermarket suspension. Not saying anything negative about the aftermarket because me personally if I didn't have a 1LE I would be looking at a full Pedder's kit.
Another thing to consider is ride comfort. I will tell you that the 1LE is surprisingly a very good ride for the handling capability it has. There are quite a few pro's and con's to consider other than "best" for the money. You also need to ask yourself if you are really going to use the car at the track to benefit from any of the more expensive aftermarket set ups. Otherwise you can get a very good handling car with the 1LE package and have money left over for other fun mods if your not a serious track person.