The problem with many of these comments is the fact that you really can't just sit down and do a respectful job on an arranger without spending hours in preparation. I love my 3000 and no doubt would love a PA4x but I absolutely love my BIAB just as much. BIAB is much cheaper with $150 yearly updates. Live musicians are much better than MIDI when it comes to sound.
If i would build a dream arranger workstation..
Band in a box would be a part of it..
Because it would be software based...
With a dedicated hardware controller..
The only thing missing in biab for integration with the rest of an arranger, is an option to send its chords out as midi notes.. so you can not really use it to feed your arranger to mix biab tracks and arranger tracks and multipads...