After comments and some email dialogue, I realize I should have been clearer in the recent MOST READ story that almost certainly both The Order of the Stick and Erfworld are on that list somewhere.
I’ve emailed back and forth with Rob Balder of Erfworld and Rich Burlew of The Order of the Stick and they state that based on their server stats that Erfworld has approximately 65% of the audience that The Order of the Stick has. Another way to put it is that about 65% of The Order of the Stick readers also read Erfworld. That would put The Order of the Stick between the #5 and #6 spots and Erfworld between the # 8 and #9 spots.
Also you may be interested in a recent FLEEN thread where Project Wonderful head honcho Ryan North and others have been discussing the pros and cons of using Project Wonderful data for the Most Read list.