Quote Originally Posted by uid313 View Post
UEFI can run in the background and can run background services behind the OS while the OS is also running.
UEFI have much more control over the system and has a built-in TCP stack.

BIOS is much more simple and can not run stuff in the background.

UEFI is much more dangerous and likely to be vulnerable, exploitable and backdoored.
I really hope you don't have recent Intel motherboards in any of your computers- otherwise, you very likely have Intel's Management Engine as part of your BIOS/UEFI. It's a very interesting technology if you are the one controlling it- it's basically another OS inside your computer that's trusted to do everything- with it's own networking stack as well. It's also hugely undocumented, and the main reason Flashrom can't be used safely on vast numbers of recent computers with Intel motherboards.