Hi Frank,
I don't actually have the s750, I have the s950. Even though I don't I like it as much as my pa3x ( not a fair comparison as one was at least double the price of the other)
I do like the Yamaha styles, and ther's heaps of them around.I would gather most of your g70 styles are covered by the bk7m anyway.
Yamaha would add some great additional styles.

I doubt the quality of the keyboard itself would be as good as the g70, considering the g70 was a top end arranger in it's day ( had a couple of earlier top end Roland's , the g800 and the va7) they were really solid.

If you're looking for something lighter and a variety of styles, it would be worth considering.

I had a psr1500 which must be close to 10 years old. Gave it to the grandkids (5 & 8 year old) a couple of years ago, and it's still working perfectly.
They must be more solid than they appear, because the grandkids are not gentle on things. Haha

On the other hand my pa800 ( which was treated with the utmost care) had it's screen go blank, after only 3 years. Cost an arm and a leg to fix.