This is a pretty good article on the advantages of UEFI:http://h30565.www3.hp.com/t5/Feature-Articles/The-30-year-long-Reign-of-BIOS-is-Over-Why-UEFI-Will-Rock-Your/ba-p/198
As with most tech topics, UEFI is having its share of controversy (do a search on "UEFI secure boot"; also, the Pope -- I mean Linus -- apparently doesn't like it
). For my money, I like it because it boots faster. Also, a standard BIOS can't boot a hard drive of capacity greater than 2.1Tb (my little Thinkpad isn't there yet, but maybe some day ...).
I made the switch when I got an SSD. SSDs benefit from GPT formatting (superior partition alignment). I read that GPT is part of the UEFI specification (see Rod's Book link below), so I decided to convert to UEFI and GPT at the same time.
One reason UEFI Linux machines can boot faster is that, since kernel 3.3, an EFI boot stub has been built into the kernel itself. In other words, you don't even need a boot loader. The EFI firmware in your machine will boot the Linux kernel directly, if you want it to.
To facilitate sending kernel options to the kernel, though, a lot of people use a simple boot manager like rEFInd or gummiboot. You can use grub2, but, as somebody who mainly just needs to boot a kernel, perhaps with a simple kernel option or two, I find grub2 unnecessarily complex. I've gone with rEFInd, which works very well.
I've learned a great deal from reading the "Rod's Books" pages on UEFI, GPT, etc. Here's one example:http://www.rodsbooks.com/gdisk/booting.html
This particular page has a good discussion of EFI vs. BIOS.
While I've spent a good bit of time fiddling with UEFI and GPT matters and trying to get various distros to install via UEFI, I'm really out of my depth to try to discuss the finer technical points. Still, I hope this helps a bit.