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Pro Support for a large number of Operating Systems
Grub can load a large number of operating systems, not just Linux.
Pro Easy to install and setup
Only requires 2 commands most of the time (i.e. grub-install ... and grub-mkconfig ...).
Pro Has an interactive CLI
Grub has an interactive command line interface which can be very helpful at times if anything goes wrong during the boot process, especially after a fresh install or after a kernel update.
Pro Easily locates a kernel file
Grub is very file-system aware. This way, it can easily locate a kernel file which is residing in the file system without having to specify a logical-sector.
Con Fully-featured also means harder to wrap your head around
Grub has a lot of features that other boot loaders may not have. But this also means more time spent on the documentation if you want to know the ins and outs of it.