Some of the limitations of BIOS are as follows:
- 1 MB address space
- Slow performance on ROM startup
- Master Boot Record (MBR) maximum bootable disk size of 2.2 TB
The advantages of UEFI over BIOS are the following:
- Security features such as Secure Boot and encrypted drives that prevent malware from running before the OS is loaded
- Faster startup and resume times
- Support for drives larger than 2.2 TB as well as drives with more than four partitions
- Support for modern, 64-bit firmware device drivers that the system can use to address more than 17.2 billion GB of memory during startup
- Backward compatibility to use BIOS with UEFI hardware, although Secure Boot must be turned off
- Support for multicast image deployments
Many current computers have the capability to use a BIOS or UEFI firmware mode—switching between one and the other is a fairly simple task. However, there are items to take into consideration with regard to OS deployment and changing existing systems that are on BIOS mode to UEFI mode:
- Changing from BIOS to UEFI requires changing the MBR/NTFS to GPT/FAT32 and NTFS. This translates to reinstalling the OS. This would be the equivalent to a wipe-and-load deployment.
- Ensure that the startup option you select matches the setting you want to have. It is common for old machines to have several startup options for BIOS but only a few for UEFI, or vice versa.
- When deploying from media, the media must be FAT32 for UEFI, and FAT32 has a file-size limitation of 4 GB.
- UEFI does not support cross-platform startup, you will need to have the correct startup media (32 or 64-bit).
- For UEFI-based PCs that support both UEFI and legacy BIOS modes, WinPE needs to be started in the correct mode in order to correctly install Windows. For more information, see WinPE: Boot in UEFI or legacy BIOS mode.
Source: Deploying Windows 10 Press Book