As far as I know every pre-order will have a head start, starting the 24th. You will also have VIP which means you are invited to beta at the 15th.
As pre-order, you also have the option to subscribe for a lower monthly price if you chose to subscribe for 3 or more months.
And last, you will get some goodies :D Mount, pet and/or bag size increase.
Now really last, you can pre order anywhere, there is no difference in region, if you buy it in the US, you can play on EU servers and vice versa.