I had the S950, own the S970...

Biggest differences, and they are significant to me:

Larger screen

Active control knobs...use them all the time

Bigger on board memory

Audio styles...sound excellent live

VCM...love this feature..a person can really shape voices with it

Speaking of voices, it does have human voices...sounds pretty good

Multipads...I like the way the multipads are organized...makes using them quicker and easier.

When I had the S950, I used it for backup and took the Tyros to gigs....10 - 14 a month.

Now the S970 is my main board and the Tyros stays home most of the time.