There are several differences between BIOS-mode and EFI-mode booting:

• On new computers, a BIOS-mode boot is likely to take longer than an EFI-mode boot (by a few seconds).
• Each mode has its own boot loaders and boot managers. In BIOS mode, you've got LILO, GRUB Legacy, GRUB 2, BURG, SYSLINUX, and a few others for Linux. In EFI mode, you've got ELILO, Fedora's patched GRUB Legacy, GRUB 2, the Linux kernel's EFI stub loader, rEFInd, gummiboot, and one or two very exotic boot loaders. (See my Web page on the topic for details about these EFI boot loaders and boot managers.) You might have a preference for a specific BIOS-only or an EFI-only boot loader.
• EFI-mode boot loader maintenance is different from BIOS-mode boot loader maintenance. Once you know what you're doing, and if your EFI isn't bug-laden, EFI boot loader maintenance is easier and more flexible; but most newbies find it harder because they're familiar with the BIOS model and because tools for managing BIOS boot loaders are better integrated into OSes and OS installers than are tools for managing EFI boot loaders.
• EFI-mode booting gives you access to EFI runtime services. Currently, this is pretty minor -- they let you manage the boot order from Linux and let the kernel store data in NVRAM in the event of a kernel panic, but that's about it. In the future, EFI runtime services may become more important.
• EFI provides a boot-time environment that can be handy for things like editing boot loader configuration files without booting an OS.
• Recent EFIs, including those that ship on computers with Windows 8, support Secure Boot. This is currently more of a hassle than an advantage for Linux users because Secure Boot support in Linux is still primitive; but it does provide at least a theoretical security advantage because it helps protect against EFI boot kits.
• Although not a BIOS disadvantage per se, switching from EFI mode to BIOS mode requires re-installing your OS(es), or at least reconfiguring their boot loaders -- at least, assuming you want to keep anything already installed (Windows, if you haven't yet installed anything else).

All of these are absolutely trivial compared to the big drawback to EFI-mode booting on Samsung laptops that you've identified: If the Samsung firmware bug is triggered, your new computer will become a useless lump.

Concerning the bit-width of Linux, in EFI mode, you're best off with the 64-bit version. Although the 32-bit version can work with some hoop-jumping, the 64-bit version will be easier to install and will work better. In BIOS mode, either version will work, although I still recommend the 64-bit version because it's likely to be faster, particularly with some types of programs.

Question:

How do you work around the UEFI BIOS issues present in Phoenix and Samsung devices where the boot process cannot be interrupted as expected with either the F2 or F10 Keys?

Context:

Also Effects: Phoenix BIOS P06AAE, Samsung NP700Z7C (NP700Z7C-S01US)

On Samsung computers, a Phoenix BIOS is present with the option to change the BIOS mode from legacy to UEFI.

However, changing to UEFI mode makes it impossible to interrupt the boot process and return to the BIOS configuration.

Normal interrupt keys don't work as expected: Escape, F1, F2, F5, F8, F10, F11, F12, Tab, etc.

Windows 10 may also get stuck in an endless Boot Loop -- if the BIOS is changed from legacy to UEFI. Windows 10 will be unable to fix its boot process, (a conflict between using the EFI system partition, and the MBR).

Resolution:

I resolved this issue by using an external keyboard:

In order to interrupt the boot process successfully, perhaps try:

At boot -- Spam the Keyboard's F10 and F11, (or: Esc, F1, F2, F10, F11, F12, Tab) ...

But use both keyboards -- the laptop keyboard AND the external keyboard -- simultaneously, alternately, repeatedly, fast --

However -- I was only able to get to the UEFI Boot Menu -- (I had an ArchLinux USB, (MBR Partitioned), and a Windows 10 Installation USB, (GPT partitioned).

I am unsure if this is simply a "timing issue" where I was able to "coincidentally" hit the right button, at the right time --

Or, perhaps it is a hardware interrupt issue -- where the external keyboard is necessary.

Issue Explanation:

Unfortunately, it does not appear that there is a new version of the BIOS released, (as of this post). And, there is not a way to get back into Legacy BIOS configuration from the UEFI menu.

Warning, Before Using UEFI on Samsung / Phoenix Laptops:

Obviously -- enable UEFI on Samsung laptops with caution.

This appears to be an issue with corrupted NVRAM in the BIOS, or just bad BIOS code.

Because there are no new BIOS updates regarding this issue -- I am apprehensive about re-flashing.

Note: Samsung's digital certificate for the biosupdate.exe utility is expired, and must be run from the command prompt. You can right click the .exe to view the certificate, and attempt to install into the trusted publisher store -- However, the utility won't overwrite / reset the current BIOS if it is the same BIOS version that it is being updated to.