I use whichever one I need.
If I'm home alone and trying random ideas, BiaB.
If I am with a guitar player and bass player, I use RB since we can all easily input our part ideas.
Depends on the job at hand and the desired outcome. Each has its place.
As for the OP original question
Quote:

Is there any advantage to using BIAB first, and then opening up the file in RealBand



Yes in some instances. You can audition styles, chord changes, song structure changes faster in BiaB. BiaB is ready to play the generated song faster than RB. I think that's because RB has to generate the whole thing first and BiaB is able to generate 'enough' and then generate the rest behind the scenes as the song plays. Plus RB requires laying out changes 'linearly' where BiaB uses choruses to repeat certain sections (although it still generates a new section for it). So RB is more time consuming to change sections that way (if the song has repeating sections) since BiaB can change the chords once for three verses or choruses or whatever.

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