As far as I am concerned, it's the NEW BK-9 features that sell it to me. Obviously, we all miss Roland being in the TOTL market segment, but as Mike points out, at half the price (or at least $1000 less) of a T4 or PA3x76, you can hardly put the BK-9 into TOTL territory.
But the Chord Sequencer is a game changer for the decent player, a welcome return to Roland's feature list after an absence of more than 13 years, and unavailable in anything else short of a PA3x or PA600. Then there are the tempo synced audio loops, and although the demos of this feature are few and far between, so far, it's the REAL game changer. So far, unavailable on anything other than Ketron (for key-triggered version) or Korg (but with a lot more work to set it up for easy use) on multipads. Yamaha's version on the S950 doesn't count yet, because the idiots left off the ability to loop the audio! Not much point in having audio on the multipads if it can't loop, TBH...
But this feature alone can push your sound into MUCH more contemporary areas... the combination of styles and breakbeat loops is THE sound of contemporary jazz, hiphop, rap and techno just for starters.
Now, from my sampler days, and from having several TOTL beat loop libraries (I highly recommend Spectrasonic's StylusRMX), it is a snap to make audio loops at precise tempos for use in the arranger. So I'm good to go... Now, if you don't have all this stuff, or are uncomfortable trimming and tweaking loops, it might be a stiffer learning curve, but bottom line is, if you have been jealous of the hip stuff WS's can churn out in the drum and percussion dept., here's the answer. Without having to buy one (and haul it around!)!
So, as far as I am concerned, many of the features missing from the BK-9 compared to my G70 are moot. I loathe harmonizers, standalones blow any in an arranger away (and Roland don't make a standalone that competes with the best of them), speakers are simply dead weight at the volumes I generally play at (and insufficient to keep up with a live drummer), I doubt 5% actually USE any sampler on their arranger... I know I won't need one! Got that all covered in the studio if I need it for recording. So never missed it on my G70, won't miss it on the BK-9.
Cheap small video monitors for lyrics can be had for WELL under $100, no need for an iPad (I fail to be impressed with the Roland iPad apps, adding little that the BK-9 doesn't already do), probably the aftertouch (and the superb G70 action) will be the only thing I'll miss.
As I'll keep my G70's for live band, the ease of the touchscreen won't be a big factor, as solo work is always set up in advance with Performances. I doubt I'll need to menu around a whole lot...
Now, you guys know I am about as big a fan of the G70 as you are likely to find, but I am not crying over the change. For strictly solo or duo work, the BK-9 is a FAR better arranger than my G70! Tough to say, but I think true. The CS and loops will change my sound and playing radically, and the 21 lbs weight won't be a burden, either!
I look forward to trying one out.
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An arranger is just a tool. What matters is what you build with it..!