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.
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.
After running the main configuration generation command, you can easily change the names of your Arch Linux and Windows entries and disable auto-boot for Linux, if you use both equally.
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.
Grub2 is the main standard in linux instalation, but when you have to install several systems it just dont work well. You end having a bunch of nested menus of systems to boot repeated.