But we're not talking about whether or not semi auto cars are faster than h-pattern cars are we? Aren't we discussing whether or not when driving a car in gt5 (that has an h-pattern shifter) using your own h-pattern shifter puts you at a disadvantage.
I agree that semi-auto transmission are faster than h-pattern transmissions. But I just did the test jjaisli suggested and using the h-pattern shifter and clutch I was able to pull ahead by a few inches before I ran out of straight on that the short suzuka track (gears 1 through 5).
I used a Lotus Elise 111r that had been tuned for the Tsukuba Expert Event on the shortest suzuka track. Before starting my control lap I came to a stop at the last grid spot on the left before the start/finish line. I then used the paddle shifters on my G27 to accelerate down the straight, shifting as close to 10,000 rpm as I could each time. I then completed the lap and then exited and re-entered so I'd have that lap as a ghost. I then did the same thing as before, stopped at last grid on left before start/finish. Accelerated down the straight with the H-Pattern shifter on my G27. Now I'll admit, I wasn't fast enough at shifting the first 3 times I tried, and if you screw up once, you lose a lot of distance very quickly. But on my fourth try I was able to pull ahead by about a foot before I ran out of track.
So...in conclusion, if you're really fast with the H-shifter, I think you can exceed the shifting speed of shifting with a button. But I'd probably say you're still at a disadvantage, the computer never screws up, and I do all the time...
Remember, I'm not saying that in real life an H-pattern transmission is faster than a semi-auto transmission. I'm saying that when you're driving a car in GT5 that has an H-pattern shifter, using your own H-pattern shifter can be faster than using a button to tell GT5 to shift it for you.