Thanks to everyone for all your input. I think it proves that everyone is different and it's good to have so many options. Thanks also to carkins for the video link, it's well worth watching the series if you haven't already seen it!

I think I'm going to work in a similar way to the guy in the video (except for Cubase instead of Reaper as the final step).

I like the idea of getting the basics down in BiaB, getting the right key, etc. and then adding further enhancements in RB (adding more RealTracks, MultiRiffs, MIDI, etc.) before finishing off in Cubase.

All I need to do now is start writing a new song!