The Xbox Store has arguably the juiciest bonus, granting a code for one month of EA Access. The code, available for a limited time, will be delivered to your Xbox message center in 7-10 days from your pre-order, and must be redeemed by November 3rd.
With this, considering that the game will be available first on EA Access, Microsoft basically ensure that those who pre-order on its storefront will have the means to gain access to the game before anyone else. On top of that, you also get access to the rest of the EA Access line-up for a month, which is certainly nice.
The PlayStation Store has its own bonus, in the form of a PS4 theme.
Battlefield 1 releases for Xbox One, PS4 and PC on October 21st, with early access on Octoper 18th provided to those who will get the Early Enlister Deluxe Edition.