I don't know the specifics...but, I believe the All Star Resorts are located in a different county than Pop Century.
I think (not sure) that you pay 12.5% tax at Pop Century vs 13% at the All Star Resorts.
I'm not sure how this works when booking a package....ie, do you get taxed 13% on the entire package at All Star compared to 12.5% at Pop?
I may be off on the %'s as well...All Star might be more than 13%....but, I do know they have different tax %'s. That should make up some of the difference.
Also...make sure that they are not trying to put you in a preferred room at All Stars vs a standard room at Pop Century. The Disney website is kinda funny about that. Sometimes it shows me preferred room first with the option to downgrade...and sometimes it shows me standard room first with the option to upgrade.
Hope this helps....
Speed