Dropping the touch screens is a HUGE step backwards for Roland. Particularly as the component price on them, compared to when they first came out (2005?) is much lower. Modern arrangers are so capable, so complex, that having front-panel buttons for everything is completely impractical (and expensive). So everything gets shunted to menus and sub-menus, and editing becomes much more of a chore.
The touch screen is the perfect answer to the problem, because one button can call up a screen with DOZENS of virtual buttons, and another button call up yet another screen. Nothing is more than a couple of button pushes away. This new system is nowhere NEAR as user friendly or fast, and those are the two things that make people USE editing features!
Trident... some of the 'sizzle' is newer drum kits, with better hi-hats, some of it is different EQ on the Parts, and more 'Mastering' Tools, but if you take all that off, overall, there's not a huge difference to the G70 other than the noticeably shorter loops on some of the major sounds... Obviously, the BK-7m doesn't have the full 192MB of ROM that the G70 said it did. But this is standard procedure for downmarket arrangers compared to the TOTL.
Overall, there is much to like about the BK-7m, compared to the G70. Drums are improved, and electric and acoustic guitars have been bettered substantially. The styles are well balanced (other than the reverb overload on some of them) and EQ'd, and I think this latter aspect is the primary reason most hear a difference to the G70. The 3-band parametric EQ per Part and per drum was an upgrade to the G70 after it had been out a year or more. And, to be perfectly honest, the styles were all made prior to that capability, and after it was added, Roland, although they issued newer styles, they seem to have taken this long to fully understand and utilize them. But many of the EQ 'tweaks', when applied to older G70 styles and kits, can help it sound pretty close to the BK series.
I wouldn't trade my G70 away in a million years in comparison to the BK-7m, and from what I've seen so far of the BK-9, I don't think this one will make me do it either. I always like to tweak and personalize my styles, and the speed and ease of being able to do this is probably (other than great drums!) my primary need in an arranger.
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An arranger is just a tool. What matters is what you build with it..!