I think the general feel is to use BiaB to *create* the song, ie find the chords and the general style you like.
You can generate all the tracks quickly in BiaB to audtition different ideas.

Then open that file in RB and regenerate those sections you are not happy with, either MIDI or Realtracks.
Change the sound of some MIDI parts to different synths that may sound better, as you can use more than one in RB (16 hardware and 16 software).
Then record any extra parts you want to add (vocals, guitar solo whatever)
Then add some EQ, Reverb or other processing to the tracks for clarity.(mixing)
Then use the output FX section to premaster the whole mix.

It *is* a lot more flexible, which of course means some learning will be involved .

I do not work here, but the benefits are still awesome
Make your sound your own!