I wish I had gotten a dyno before/after I put my shorties on. So far, that has been the single best mod I have made. I noticed an IMMEDIATE increase in throttle sensitivity and power (especially above 3500rpm).
I really don't know what it would feel like to get LTs put on, but I really can't imagine it being better than the way the shorties felt. I've found in the past that it takes about 20-25 horsepower to be able to *feel* a difference in your car...which leads me to believe that I picked up at least that much. Unfortunately, I cannot prove it since I didn't get my dynos done, so you'll just have to take my word for it.
Now...people HAVE proven that the LTs can give you up to 30 horsepower, so if you want the maximum performance, you really need to go with the LTs.