Yo ...Dave !
Here's what I know .
While using the styles , there is not a dedicated fill in button . You must touch the screen and than turn the dial to move to 1 of 4 variations . Not easy for live performance IMHO . The action is the same action as on the just released SP200.
Korg recently started using Fatar actions , instead of YAMMY . The action is better than what Fatar has previously made . But not as good as Yamaha or Roland IMO.
The styles are classic Korg styles . They do offer "ensemble" feature to harmonize the right hand sound . There is also a dedicated button for small ensemble ( lees parts of pattern) .
I would say that the keyboard is a better value than the FP3 .
$200.00 or $250.00 price difference between the 2 products . You get more recording and much better drum loops with the SP500 and it's LIGHTER to carry . It looks nicer than the FP3 as well ! dano