Since the Disney Club is no more, there are no discounts on annual passes or premium passes (unless you are a Florida resident and are interested in some of those options). You can only buy annual /premium annual passes from Disney - none of the other ticket brokers are allowed to sell them.
It doesn't matter where you buy them - the price will be the same. You will pay the Florida state tax on your purchase and no other state's sales tax.
If you buy them at a
Disney Store, online or via phone, you will receive a voucher that must be activated at one of the parks. Your year will not start until the pass is activated. If you buy online or via phone, the vouchers will be mailed to you. There is a $3 charge per order to cover the costs of mailing.
I usually buy mine at the Disney store, but only because I like to have some trip expenses paid ahead of time. There isn't any advantage to buying in advance unless you think Disney will raise tickets prices before your trip.
ere's a link that will tell you all the places that sell annual/premium annual passes:
Purchasing Tickets
Best wishes -