You ask how easy it is to CREATE styles on them...

Do you create styles now, or have you in the past? If not, be warned it's a LOT harder than people make out (unless by 'create' you mean assemble styles from other existing styles). In fact, MOST people that say they create styles actually 'assemble' them then do minor surgery, not create out of the blue.

From what a lot of the Korg people say there is NOT much in the way of third-party styles for the Korg. What you get is probably what you'll have to use, at least for quite a while...

If this suits you, you're OK. If the ROM styles don't cover enough of your style base, you might need to consider something else...