I might sell ONE of them..!
I'll never sell both, until maybe Roland make a real TOTL BK based keyboard, with the pro action and touch screen from the G/E series. I do a LOT of live band work, and IMHO, no keyboard has ever been made that is easier to work with on a live stage. And that includes workstations!
When you don't have the luxury of setting everything up in advance (which you HAVE to do with all modern WS's), finding the right sounds, splitting and layering the keyboard, applying the right effects, and getting the volumes and balances right, and doing all this in just a few seconds while the band counts off a song is critical. There simply hasn't been a keyboard made that can do this faster than the G70, and its primary meat and potatoes sounds (grand piano, E. Pianos, Hammond's, brass and strings and synths) are still some of the very best in any keyboard.
Sure, some of the newer WS's can exceed it in these areas, but there's little use for a great piano sound if you have to miss the first verse trying to set up a piano/organ layer in the LH, and a swell brass/sax in the right, with an echo timed to the tempo of the song!
I will, however, probably be using the BK-9 for solo and duo work, as the Chord Sequencer is a complete game changer for those of us that like to solo (and it will make it easy to use my trombone in an arranger setting) and want a more contemporary sound, thanks to the audio loops.
Both my G70's are still pretty cherry, so some lucky guy will make out when I have to unload one!
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An arranger is just a tool. What matters is what you build with it..!