Thanks for the test, happy to provide the inspiration and assistance!
Using the same T60 and Z61t I had on hand yesterday with both booted into Windows 32-bit, and, as indicated previous, very similar units spec wise beyond CPU, observed over ~5 minutes:
T60 (T5600 @ 1.83 Ghz, 2 GB RAM, Intel 950, Win 7 Ultimate SP1 32-bit + all updates, Flash 11.2.202, WD Blue 5400 RPM HDD, 15.4" WXGA):
FPS (Full Screen):
Highest: 28 (Staying mostly at 26-27.)
CPU Usage: Up to 85%
Z61t (T2500 @ 2.0 Ghz, 2 GB Ram, Intel 950, Win 7 Ultimate SP1 32-bit + all updates, Flash 11.2.202, Toshiba 7200 RPM HDD, 14.1" WXGA):
FPS (Full Screen):
Highest: 25 (Staying mostly at 23-24.)
CPU Usage: Also Up to 85%
And for a fun comparison, here is a T420 I have around right now (i5-2520M @ 2.5 Ghz, 8 GB Ram, Intel HD 3000, Win 7 Pro SP1 64-bit + all updates, Flash 11.2.202, Intel 320 SSD, 14" HD+):
Highest: 40 (Staying mostly at 40.)
CPU Usage: Up to 30%
Are you referring to the flash test above, or in general? If the flash test, than you haven't tested them under even remotely the same conditions, if I understood your post correctly. If in general - do the machines also have the same hard drive and the same OS installation/configuration. Software / OS configuration has a tendency to affect performance even more than hardware.
Flash test wasn't up yet, so that was simply my experience, like I said. Regarding the software & OS, this still supports my assertion: C2D allows you to run 64-bit which nowadays will translate into a performance improvement for many programs.
If there's one clear conclusion I think we can all agree upon it is this: the ATI chips have not aged well at all.
And from that, I stand by my most preferred recommendation option to replace the MB with one that has Integrated graphics and a C2D already on it, preserving the beautiful FlexView. Going by our numbers, that move would significantly improve the OP's flash performance, if nothing else.