While I've been steadily plugging the 2008 O2C Doeberl Cup, there is also the 2008 Sydney International Open to look at as well. As of Friday (the official closing dates for SIO entries), the SIO had 101 entries, while the SIO Challengers had 47 players. In terms of Grandmasters the SIO comes out in front of the Doeberl, with 3 extra GM's playing not making the trip to Canberra. They are Chandler (NZ), Zhao (although he still may appear at the Doeberl) and recent SIO entry Antonio from the Philippines. Apart from that the fields are similar in rating (with hardly a difference between the rating of the 30th and 40th seeds in both events), even if the players aren't quite the same.
(Usual Disclaimer: I am an official at both these events)