You're asking about two different things. The advantages of EFI as a whole to an ordinary end user are quite considerable, but they are not of the form where one can invoke something directly and say "that's EFI". They are indirect. Because the firmware is more regular, more self-consistent, and less encumbered by tight architectural constraints, system softwares (that use the firmware) are easier to write, and simpler in operation.
The EFI Shell is only one of the facets of EFI — alongside the boot manager, the partitioning scheme, and the firmware proper itself. The advantages of the EFI Shell are few to the ordinary end user. After all, ordinary end users don't maintain the machine.
The advantages of the EFI Shell are more for system administrators. The Shell comprises a pre-boot environment where a system adminstrator can do basic file, disc volume, and device manipulation tasks. Some of the earliest EFI utility programs for x86 were EFI versions of CHKDSK
, FORMAT
, and DISKPART
. On more mature EFI platforms, the toolset now available is larger. However, the toolsets are aimed at the sorts of things that system administrators need to do, rather than ordinary end users. There are no word processors, for example, but there are tools for editing the raw contents of a file or disc volume in hexadecimal.
efi capable OS can boot faster via EFI than via legacy BIOS, since it does not have to go the whole 16-bit -> 32-bit -> 64-bit route. and installing a new OS creates less driver issues. however, most end users will never install an OS nowadays (or even boot from a removable disk), so I only put this as a comment here, not as an answer :) – mihi – 2011-09-07T16:55:40.070