I agree that there are some subtle considerations...
For me personally it came down to bulk. I don't play piano, so I can get by without the G-70's top-quality 76 keybed. Also I'm not a big guy, and and I just didn't want to wrestle with a 45-lb. arranger.
According to Diki (remember him?) the BK-9 has better mastering tools, and of course the chord sequencer. I have other instruments with the ability to create and store a chord progression, and I seldom use it. It seems like the start of a slippery slope toward playing over recorded music, which so far hasn't been part of my approach to the hobby.
The BKs and EA-7 allow styles with multiple drum tracks. A style like this won't play on the 'G' (although the styles on the G-70, and even older Rolands sounded pretty good, so the improvements are incremental.)
My last area of concern is parts/repair. If you pay a low enough price, I guess that mitigates the risk of failure. But if you buy one and really like it, you had better buy a second one for backup. Because if something goes wrong you may find yourself looking for another board!
Ted, a difference of opinion about comparing the BK9 /EA7 to the G70..
Yes you can take an acc style part and assign a drum kit in style composer. You cannot do this in style composer on the G70, but there is a better and a finished product way of doing this..
If you want to record your style using the added drum track, and save as a song .. This is easily done with the G70.
You can midi capture your song by playing in arranger mode.. Open your 16 track sequencer. Select the track /channel you want to record drums, and sequence the data..
If you want to use a factory style that uses a 2nd drum track
The G70 will load it and play it(with a tone instead of a drum..) Simply open the 16 track sequencer and change the instrument to a drum kit that matches your style. It will play the style as a son g format the same as the EA-7..
BTW: I have never came across a style that used 2 drum tracks worth using.
Secondly the EA-7 could not do any of the above that the G70 does..
It has no MIDI capture or a 16 track sequencer.
Your BK9 can , it has both..
As for the mastering tools, I don't know of any difference.. The G70 allows you to bring parts out of a separate out and run into the audio input, then you can add additional effects before mastering..
You cannot do this with the BK9 or EA7..
Just wanted to show it with a better understanding..