I wouldn't buy any of them but that is not to say you shouldn't. If you are gigging with it I do question the longevity of mechanics inside these with the least worthy being the Casios, IMO. The Korgs might be worth while but it matters how you connect up your sound and how it goes FOH. For instance as I recall the SP170 hase no 1/4" TRS out. It matters if you will use internal sounds or virtual sounds via mixer or programs. Will you use midi ?