Reliable population stats?

[Emperor Newt]

I was interested to see what OMFG did for the overall population on my server (Miller). So far I know two websites providing population data:

http://sirisian.com/planetside2/popu...=10&timezone=0

and

http://www.therebelscum.net/world-po...&totalpop=true

Problem being: if I look at the peak times the total pop differs by over 500 players at times. So any ideas why that is and suggestions which data to trust? Are there other sources to use?

*edit*
Doh! Stupid me. At Sirisian it states:

The data represents the number of users that were logged in during a specific hour. This number is slightly larger than if you took the exact number of users currently logged in at a given hour since users could log in and play for a small amount of time. Take this into consideration since you can't use this data to say that at a certain time an exact number of people were playing.

So if I get this right the Sirisian data "overestimates" the amount of people as some of them could only be logging in for their daily certs etc but are not actually be playing. So the numbers grow although those players have never "participated" and should not be considered "active"?
So if I want to have a more exact feeling on how the active population developed the "RebelScum" data should be better?