I have used PDAs from the old Wizard, to Palm (III, V, IIIc), to PocketPC (HP iPaq 3395, 2210).
Every time I've switched, I got attracted to the extra non-organizer programs, but ultimately ended up using each PDA for basic calendar/contacts/etc functions.
Honestly, right now, a jailbroken iPod Touch is the best PDA to use with a Mac. I cannot stand MissingSync (it's hit-or-miss when it works, plus there's been 3 pay updates in the past two years), which is needed with a PocketPC (and can be used with Palm). The Touch's interface for Calendar and Addressbook are very similiar to the iCal/Addressbook counterparts in OSX. Everything is quite seamless and works well.