Are we just talking about Linux in general?
I have never done anything but the MBR. My understanding is that the primary reason anyone would install the bootloader into a partition rather than the MBR is incase something went wrong during installation. In the early days, Linux bootloaders were not quite as reliable, so the idea was that if it should fail, your MBR would still be workable and you could boot to another partition/OS.
I could be wrong about that, but surely the default on modern Linux systems is to go straight to the MBR.