I agree with angelb... it depends on what you want...
"better" is a matter of opinion...

GPE
PROs
--2 way sync with google calender (via erminig with some limitations)
-- GPE summary Applet

CONs
--kinda clunky visually (personal preference)
--GPE Summary uses a large portion of the screen
----& is hard coded for font / background color & no transparency

--alarms don't work well (if at all--I don't use the alarms on the N800)
----(I get my alarms via SMS from GCal)

Gene's PIM suite
PROs
--I believe Alarms work (although the Cal app launches at Midnight for housekeeping, and then doesn't always shutdown)

CONs (for me)
--1 way sync to google calendar (subscribe / download import ical)

For me the 2 way Google calendar sync was the deciding factor...

For Contacts I have ended up using Gene's InfoOnTap database rather than a "real/dedicated" contacts list as I don't need the integration with the tablet email/chat etc. (I may just make a spreadsheet file and use Gnumeric, Undecided at this point)

ToDos I have the GPE ToDo installed (but not used much) I tend to use Jott / Remember the Milk / Google Cal from my cellphone

Memos / Outlook notes
--Notecase (on ITT and Windows)

So to answer your original question... There is NO "best" PIM.