migo... I have to say that, judging by the population of this thread, my own personal experience, and the general attitude I have observed across the internet, you are wrong.
I mean, I'm not saying that the DualShock design doesn't work better for you; ergonomics are entirely subjective, and there is no such thing as a "correct" ergonomic design, since everyone's hands are different. But the grand majority of people, including myself, prefer the 360's layout.
I have both a PS3 and a 360, I spend a lot of time gaming on both, and I have to say that I, personally, vastly prefer the 360's pad. I find it more comfortable in my hands, and I have always found that I perform better with the 360's analogue and button layout. The majority of your argument seems centred around the fact that, while using a 360 pad, your thumb is extended further than it is on a DualShock. That is an undeniable fact, but I see it as a plus, rather than a negative; on the DualShock, my thumb always feels too bent over, too cramped, whereas on a 360 pad I feel perfectly comfortable.
Now, as I said earlier, ergonomics are entirely subjective, but the vast majority of people in the thread, and indeed over the entire internet, seem to prefer the 360's design, as I do.