Earlier quoted context omitted.
amd64 images use BIOS or UEFI. Macs use a variant of EFI (an earlier version of what's now called UEFI), they apparently can't cope with multi-catalog CDs and the MAC variant images fix this. See: http://askubuntu.com/a/40480/117820
Can anyone talk about how well a Macbook Pro copes with the UEFI version of Ubuntu? Fedora 20 on a 2009 13" MBP is an unfun experience. Using the UEFI boot means you get broken graphics drivers. Using the regular boot means you have to hold boot to get the image boot menu every time you power on. (I think - I could easily be wrong). You have to make sure the disk is blessed otherwise there's a large boot delay. (Fedo…
I don't know if this is still a case, but I was unable to use the proprietary nvidia drivers booting in pure UEFI mode (not BIOS compatible mode). I know that they've done a tone of UEFI work in grub/linux since then, so it's possible that this is no longer an issue.