IMHO, don't be worry, currently only 2 benefits by using UEFI .
1) If you using UEFI you can use hardisk larger than 2TB as a
"bootdisk" ,
2) you can also use the Secure Boot function.
Else i don't think there are much differrent function from Legacy BIOS.
means that, if your system only has one 3TB hardisk, and you insist to use it to install the window (the OS MUST be x64 version!), and then you need a UEFI BIOS. Actually most people now using SSD as bootdisk, i haven't seen any SSD that larger than 2TB yet, so it should not be a problem.
and, yes, UEFI mode is more advanced and convinience than Legacy one. for example, if your win8x64 was installed in UEFI mode, u can directly reboot the from windows into BIOS without pressing the keyboard. ...blah blah blah... (btw, in most of the case, we can live with or without it.)
I made a here ( http://forum.giga-byte.co.uk/index.php/topic,12871.msg83925.html#new ) where I say my GPU only runs in the PCIe "Legacy ROM" mode and not the "ETI-compatible ROM". I'm having a hard time finding out what exactly the difference is using Google, probably because I know only basic computer stuff.
....
