Funny you should mention that, Parnelli. I used a bone-stock (not even an oil change) Corvette '62 (C2) in the 1000 Miles! championship some time back, and I learned that there was a MUCH better time to shift for acceleration than at the typical redline. This car hits its power peak around 4,500 rpm, and it actually doesn't redline until much closer to 6k, so shifting at redline means that there is a LOT of revving done with far less than optimum power. For myself, I found that shifting near 5-5.5k made for much faster acceleration with the original 3-speed transmission, but it still had plenty of power to get up over 200 km/h.
Knowing your car is very, VERY useful, indeed.
As for answering the original question, I prefer manual. IMHO, it connects me to the car in a much more "real" way.