The one thing I really love about EFI on non-macs is that you don't need a boot loader. You just compile your kernel with an EFI stub and whatever you want in the initrd and then select it with the firmware GUI. That's nice
I didn't understand a lot of what you said. Any sources?
With the old BIOS-based boot process, the computer (the hardware/motherboard; not the operating system you ran on it) would, when it started up, look around for installed operating systems to boot. It wouldn't look too hard: on each hard disk, it would look in one (or, if you were lucky, four) places for a specially-prepared segment outside of the data installed by the operating system. This segment isn't a file or something that you can browse to normally on the drive (though some things shimmed it so it appeared thus); it's a non-file special segment outside of the OS's normal data/files. That segment (well, segments, but still) had to be set up just so otherwise the computer (BIOS) wouldn't find your OS to boot it. Doing this was often tricky, even more so when you needed multiple operating systems to be bootable. Doing this was also pretty inelegant, since if you wanted to stick an operating system on a sub-partition of a disk, as part of the installation process you had to mess with data that affected everything on that disk, not just what was in the sub-partition. It worked, and was simple, but it was the equivalent of being forced to modify a single central global variable in a software project every time one sub-part (file, function, whatever) of that project wanted to use a new library. For an excellent writeup of the gritty details of the BIOS/MBR startup process, see this document: https://neosmart.net/wiki/mbr-boot-process/
UEFI, put most simply, looks around for installed operating systems a lot harder than the BIOS method did. It does a lot more than that, but the benefit GP was describing accrues from UEFI being much more capable in terms of discovery: instead of checking a single global prepared location for bootable OSes, UEFI can look in the files on the drive and do the intuitive thing: "looks like these files are part of an operating system; I'll give the user an option to boot from it".
This doesn't always work perfectly, and there's a lot of complexity (and criticism) I'm hand-waving away here, but that's the gist of the difference.
Sorry, turned out to be a not-so-short version.