Don't get me wrong. I don't want to push you to Formula.
I also think that your best bet is the IS150, especially if you want to obtain a more slalom feeling.
And I also think that you deserve a correct answer of SB on the question about the difference between W and WC. My insinuation about knowing the answer referred exactly to this topic. I see that you opened a new thread for this. Very clever. I'm very curious about the answer. Let's hope SB gives an honest answer, which is often in contradiction with the commercial answer