are you asking about creating encrpyted filesystems via diskdrake
yes, diskdrake use benbi. Manually, via cryptsetup (luks), I can choice and on mga5 I had a chosen "plain" initialization vector.
According to the information I found, the difference between them is that "benbi" uses "big-endian" and "plain"/"plain64" uses "little-endian" bytes order.
Intel and AMD processors uses little-endian byte order so maybe work faster with luks encryption plain initialization vector. But maybe there are other reasons, e.g. better safety to use "benbi".