The 1.25 GHz Threshold Worth Considering?

For older or slower G3 and G4 computers, my experience is that OS X (including the latest Panther upgrade) is much faster when processor speed is 1.25 GHz or higher, and that OS 9 is quicker when processor speed is 1 GHz or less, all things (especially physical RAM) being equal.

Given that OS X now is fully efficient on computers as slow as my glacial 366 MHz Blueberry iBook, should owners of old/slow Macs keep using OS 9 for routine computing, and switch over to X for specialized tasks such as iPod/iTunes synchronization? Or should we migrate over to X for its snap, crackle, and pop, in spite of inherent processor delays?

Thanks for your comments, relevant or otherwise.

[Nemo]