I presume it'd be much the same, since both controllers have four action buttons (X, Y, A, B and X, [], O, /\), and when MO was still for the PS2, Lanning did say that the pressure sensitivity of the Dual Shock 2 would be utilised. The XBox controller is apparently also capable of this, because it allows two functions to go on the same button (even though they look like roadkill Smarties) by responding to the pressure used.
Edit: I managed to find pictures of the controllers so you can see the similarity.
XBox Controller (see what I mean about the roadkill Smarties?)
Dual Shock 2
As you can see, they each have a D-pad, two thumbsticks, start and select buttons, and four action buttons. The only differences are that the Dual Shock 2 has four L and R triggers, whereas the XBox controller only has 2. However, the XBox controller has two additional action buttons (the black and white ones) which the DS2 doesn't have.
The DS2 also has a button to toggle between Digital and Analogue mode. The XBC doesn't need this as all the XBox's games are analogue by default, whereas the PS2 is a backwards-compatible machine that needs to be able to play PSX games as well, and there are some PSX games which don't work at all if you try to play them in analogue mode (AO, WipEout, WipEout 2097 etc).
[ January 29, 2002: Message edited by: One, Two, Middlesboogie ]