Haven't seen the Korg, but the 740 would be hard to beat in that price range, particularly if you are a vocalist.
As Beakybird and George said, it is extremely easy to learn and operate. I feel one feature that I found outstanding is often overlooked, at least in these discussions.
It has a "Groove" button that effectively doubles the number of styles. For instance if you are playing Style 49, 4/4 rock and roll, you can change it to a shuffle with the touch of the Groove button.
I miss that on the PSR9000. On that keyboard you must go to a style composing page, make the groove changes, and then save to disk or flash rom.
Don