There is nothing that BiaB has to offer that can replace my Arranger Keyboards for my use.
NO WAY, because as I see it, BiaB is a PC/Mac software to write in chordprogressions to create backingtracs / playback.
I can imagine that it's a great tool for those who act like karaoke singers, to create studio recordings or for those that don't play any instruments themselves.

When use 'Autocomp Arranger Keyboard' and play live, you're free to improvice and add i.e. lenght to a song on the fly if the crowd, listeners or you want to.
You can even swap song that fit to the style in the middle of a song, or even chose another style and chord in a blink of an eye.
How do you do that with a BiaB mp3?
When playback a mp3 or waw file you're a kind of glued to that recording from start to end.

Btw, is it possible to play and control BiaB live with a midikeyboard?