The PS2's scratching is allot more accurate. But the touch sensative wheels take some more getting used to when you upgrade from a PS1. The three biggest things you will earn by upgrading from the PS1 to the PS2.
1) The Power Tuch - touch sensative jog wheels.
2) Beat juggle mode - I use it all the time, and love it.
3) Master Tempo - Change the pitch without affecting the key of the song.
Also a wide +-100% pitch mode.