I've got OS9 on both my iBook (Graphite, 192MB) and my beize G3 (266MHz, 64MB). Have WorldScript support for both Japanese and Simplified Chinese installed on both. When I create a document using either language, the iBook prints it as fast as any with just single-byte characters, while on the G3 the hard disk grinds and grinds and it takes forever (much, much more than could be accounted for by differences in processor speed or, I believe, memory).
This is true both for MS Word (which doesn't really support the multi-byte scripts well) and AppleWorks. Oh, and I'm printing to the same printer (an HP laserjet) via ethernet and lpr in both cases (lpr because the cheap Intel print server I'm using doesn't support Appletalk well).