From Rosetree's comment: "BK-9 has everything the G70 had, and much better sounds in addition, with the exception of the lack of an SRX slot."
That's too bad. It would have been great to have slots for the SRX expansions. Better yet, it should have had all the sounds of the SRX boards built-in. In your case, however, you have the Integra-7, so it's not a problem.
Thats not entirely true, the G70 also has a vocaliser on board, which is not on the BK-9, also the keybed of the G70 was awesome, i dont know if the same keybed made the BK-9.... and there is more... The G70 had 1bass , 2 left and 3 right hand sounds... Which is still the most of any Arranger out there.... Also the G70 had some nice style features, cover and make-up tools from which atleast 1 didnt make it to the BK-9 and some more smaller features which didnt make the BK9
Stating that the difference is only the SRX slot, falls short by half a mile, and not really fair to the venerable G70 that was way ahead of its time when released...