The S970 and the Pa4x are both great keyboards – but they do a different job. People do know the difference in what they hear – it is not the instrument sounds they hear but the drive and excitement. One makes you want to dance more than the other. So people in a nursing home job will be satisfied with either keyboard.
If they are out there dancing or wiggling in their wheel chairs they WILL hear the difference.
Bottom line; A good musician can do a great job with either keyboard.
Good performer + Pa4x = One great job.
Good performer = S970 = One nice job.

Only my opinion, John C.
PS, I had both keyboards in my home – there is a difference of weight. I bought the Pa4x and I am back to the gym; there is not that big of a difference between keyboards.