Very cool to see the two identical cars, different years, great pics!
I did drive both in auto though. I have also driven the 2007 Mustang Hertz Shelby.
The SS has a noticeable increase in power over the LT. The Hertz SHelby felt faster than the LT by a little bit, maybe the weight, but not as fast as the SS.
I would say, wait a bit and get the 2 SS. The two places that the Mustang has the Camaro beat is in the Dash Light "My Color" Feature (if you even had that option), and the stock exhaust sound. The Camaro SS is very Quiet compared to the Mustang. I will be doing the exhaust within 4 weeks of picking the car up...............without a doubt.
Good luck with your decision!