In my opinion I agree with what a lot of people are saying here in that if you have an SS trading in for a 1LE is likely not worth it. If I were buying new, however, the $3500 price increase is insanely cheap for what you get and I would def get a 1LE.
Since I got my 2012 SS LS3 I have been mod'ing it and when the 1LE came out I noticed it has mostly what I was looking at mod'ing.
I have put on coil overs which are better in that you can adjust the height and the damping. Adjusting to a more aggressive damping makes a huge difference if you don't mind every day driving having some feel.
Once I upgrade to ZL1 sway bars and add front and rear bushings I am sure my SS will outrun a 1LE without a doubt with regards to suspension.
I also am swapping my final drive to the 3.91. (oh btw the higher dyno numbers for a 1LE should be expected with the torq increase of the higher final drive. Our engine should be equal at the crank not the wheels.)
With these mods and the engine mods I have done (long tubes, CAI, tune, Throt body) I should be able to crush a 1LE. So yes it really has to do with what you want out of the car. I spent more money but will have a much better car. And with the same mods it kind of comes down to two things: the coil overs verse the stock 1LE mono tubes you likely wouldn't buy then swap out and the transmission gearing which I am not convinced once you go to a 3.91 final drive makes any real difference. So because I wanted to go well beyond trading to a 1LE is not worth it. Just invest the money in coil overs, sway bars and a final drive and you can equal or likely even beat a 1LE.