The advantage to having bootmii installed to boot2 is that if your wii can in fact have it installed and it does have it installed, it does allow you to be able to recover from any type of a wii file system brick. Boot2 loads before the system menu, and boot2 is always present unless you have some major crazy unexplainable screw up happens (really almost never happens. its rare chances and you dont ever need to worry about it)
Bootmii installs itself into boot2 and it tricks boot1 into thinking that it is the most recent boot2 version. It does this by the fact that there is a possible 3 spots that bootmii can be written on to the NAND, all between working blocks 1-7 (when you consider that the first block is block 0). Normally boot2 is written in blocks 1 and 2, and also blocks 7 and 6... and I say that in reverse because the placement of the blocks is in reverse. But there is also the possibility for boot2 to be written in block 3 and 4, and thats where bootmii gets installed.
I don't know/forget the details, but somehow bootmii in boot2 tricks boot1 into thinking that bootmii in boot2 is the most recent version of boot2, so boot1 launches bootmii instead of the normal boot2.
ok, that was a long winded post.
