Skills for what though? I don't play in arcades - they don't even exist anymore. So I'd just be shelling out a lot of cash to make setup for fighting games cumbersome and wipe out 20 years of existing training to make me suck again.
I think before making claims like that, you should at least have some kind of argument to back it up. A controller so big it fills the hands, domed buttons, and offset sticks are not more ergonomic (maybe if I hooked my thumbs under the controller, used my fingers to press the buttons and had 2 thumbs on my right hand...) Also, how is the DS3 outdated? It fit my hands perfectly 14 years ago, they haven't changed shape, and it has exactly the same buttons as the 360 controller. If anything, the latter is outdated because it uses big old AAs and doesn't have a rotation sensor. Really, neither are because they're for current systems and they don't remove features (beyond removing black and white buttons on the 360.)
If you play a game like DJ Max Portable, it'll become obvious why you'd want flatter, low-profile buttons and a controller you can float on your fingers without palming it. A bulky controller with tall buttons only hinders agility.
Besides, by your logic, wouldn't all these "DS3 defenders" also reject the Wii, DS and Vita since they're far more radically different than just a chunky version of the DualShock? I've used controllers since the standard was a numpad and joystick with buttons on the sides; I just prefer the DualShocks because they're more comfortable and in my hands, more effective. The 360 controllers aren't unusable like "The Duke," but they are a bit behind for general use in my experience (bad d-pad, twitchy sticks, etc)
The DS3 was never designed for thumbsticks. Originally it had no thumbsticks.
The thumbsticks were a tacked on afterthought of the original PS controller and they're not in a great position because they were just an attempt to catch up to the N64.
The Xbox has the thumbstick and buttons in the comfortable position because in most games those are what you need direct access to. The triggers hold your finger and they don't slide off as easily and the convex shape of the DS3 sticks is just silly. My tumb isn't concave.
Even the grips are more comfortable than the DS3. The original PS grips were a bit harsh and narrow and they've become slightly softer and more round with each iteration of the DS but they're still not as comfortable or well shaped as the Xbox controller.
You'll also notice that the thumbstick and buttons are almost equidistant as are the d-pad and thumbstick on the xbox controller making it comfortable to shift back and forth. The tumbsticks fit closer to your hands than the buttons and D-pad on the PS3 and it makes you have to shift your grip or pam the sticks if you're going back and forth. Anther non-ergonmic feature.