If you used an upgrade to purchase your phones online, the upgrade reversal takes up to 72 hours for some carriers.
If you purchased full retail price, Apple Retail may not be able to sell you the device for full retail price; for a few months with iPhone 5 last year, full retail price options for Verizon and Sprint were not available in-store. That is, you had to purchase iPhone 5 with a contract renewal through Apple Retail. [I bought a 16GB Gold Verizon 5s full price.]
I think it only makes sense to get in line at Apple or any other retailer--after successfully placing an order online--if you purchased online at full retail price. Keep in mind that return policies / restocking fees vary by online retailer, so be ready to eat some losses if your online order cannot be canceled and if you have to make a return and face a restocking fee. [Verizon has a restocking fee.]
Good luck.