I ordered my iPhone 6s Plus Gold 128GB at 3:15 EDT for
September 25 delivery!
I got it through the Apple Store App on the iPhone.
Apple's website store
still isn't open at 3:40 EDT, and AT&T's website shows delivery dates between October 16 and October 23 as of 3:26 EDT, so ordering through AT&T definitely has a later shipping date than ordering it through Apple. I remember the exact same thing last year. I ordered both through Apple and AT&T, then I canceled the later delivery date order.
Update: As of 3:49 EDT, I checked shipping times through the Apple Store App and it's still September 25 for the Gold 128GB iPhone 6s Plus (and some other models as well).