Well, I have a 128MB TI4200 8X 250/513mhz and it gets 1000 points less than the 9600 at the oc'ed speeds gets. I used the Det. 56series. Get 11,240 on the 9600 and around 10,500 or so with the 4200. Using very old drivers I got the 4200 at 12,176 but I believe the visual quality was below average for the default settings. The visual is just better overall to me with the Radeon with AF at 16x and AA at 4x. The 4200 doesn't support af at 16x from what I can see. And it slows way down when you enable AA on the 4200. The radeon doesn't slow down as bad as the 4200 does when you enable AA.
This is all with my limited experiance with the 9600 and 4200. I think I am going to keep the 9600 over the 4200. I am not sure yet.
Jason