With the setting set to 'Auto', the board will check to see if there is a <2.2TB boot HDD installed. If there is, it will select EFI mode. EFI mode, coupled with Win 7 64bit will ensure that you can boot from this device. If the HDD is >2.2TB, then it makes not difference.
Personally, running a Ubuntu / Win 7 dual boot setup like I do, I've only ever had problems with EFI. You might be able to get away with it with a Win 7 only system.
By the way, the EFI/Non-EFI setting only makes a difference when you do a virgin install of W7.