BB -> RB -> Reaper smile
I just made a Tip for this:
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=446843#Post446843

As for other features in RB, you've already noticed the biggest reasons to use it in your workflow.
A couple more may be the other included extras; sForzando, Sampletank, MIDI editing (with data filters), .. multiple synths/ports .. audio editing before going to Reaper (to save time) .. more mixer/routing options than BB .. lots of reasons to incorporate it as another tool in your toolpouch.

Edit:
I've had BiaB for much longer than 3 years and I am still learning with it also.

For projects, I find that I make progress faster when I move to RB sooner.
I get the basic idea down in BiaB, then right away move to RB to refine the idea .. then off to your DAW of choice to finish up.

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