After a long break I decided to buy keyboard again. I had an idea of what is "good enough for me" and so, my friend Youtube convinced me to get PSR-S670. The fact, that S670 is bottom of the line Yamaha arranger, didn't bother me at all -I'm not a snob and price was just perfect. Yes, I was very happy with S670 capabilities and quality. Still, just after few months I decided to buy S775... because display on S670 is just darn too small. And also having such low resolution, it's almost unusable for working (arranging) with it. Yeah, nobody mentioned that important fact on web.
Almost double priced S775 however, has great display.. But all buttons are made of rubber (imagine $130 Casio) -because of that, buttons "wobble" freely when pressed. And because there's no "click", it can (and does) happen, keyboard recognizes single push as pushed twice. Rubber is also harder to clean, though. S670 is premium keyboard in this regard.
Ok, why newest (better) keyboard?
Because there might be things we just can't live with (see above) or, when we exploited capabilities of keyboard we currently have. In both cases, when looking after successor, we pay most attention to avoid "flaws" our current keyboard has. Again, usually we get the best we can afford.
Yes, Genos has "real" buttons, however it has another flaw: too expensive for me
On the other hand, when Genos II arises, some current Genos owners will say "At last -that's the keyboard I was after since my birth"