We have both at my company
We have about 20 PDA users at my company. The developers and support techs seem to tend toward the PPC while sales, marketing, orders and HR folks tend to favor Palm OS.
The general consensus at my company is that the Palm is easier to use and that there are more GTD-oriented software choices for PalmOS. The PPC crew likes the native Outlook functionality, the ability to run a terminal session (hey we're geeks!), and the Today screen.
Among the PPC users, PocketInformant is the number one third-party app used.
On the Palm, Bonsai is pretty popular. Most Palm users here do not use Outlook, BTW.
FWIW, I've heard many complaints from the PPC users about ActiveSync problems.