[CentOS] CentOS 6 - Does EFI have an impact beyond the boot sequence?

Hello,

I am using an up to date CentOS 6 x86_64 laptop (Thinkpad X220t) and
after struggling a bit I could install it a few months ago with a pure
EFI boot.

However, I am not really satisfied with such things as stability,
power consumption, etc. and now that I have a little more time I want
to investigate these issues thoroughly.

So, my questions are:

- Does EFI impacts other things than the boot sequence? (a friend of
mine told me that this is a complete replacement of BIOS, and thus
impacts "everything")

- Could it change (improve?) stability, power consumption, etc. if I
would reinstall CentOS 6 using the traditional boot? (or is it just a
legacy wrapper around an EFI "BIOS"?)

Thanks in advance for your advice or for providing more details about
what you know about EFI pro and cons!

Cheers,

Mathieu