Some other differences are....
PSR S950    25 Audio Styles   vs
PSR S970    40 Styles
Flash Memory for Expansion Packs 
PSR S950 64 Megs
PSR S970 512 Megs    only 8 times more memory.  
 Tone generation on the String choir section, now it has several REAL human choirs that in the PSR S950 did not.
Besides the differences already mention like from 5 inch LED Screen to 7 inch TFT Screen, 2 Live controls, much better DSP (Digital Signal Processors=Effects), more styles, more voices, etc.....
Just my 2 cents....   
