Well to answer your question, which one?, directly: The Kastle.
Really it's a no brainer.
If you include factors like price, which you haven't mentioned, the choice is obviously more complicated.
If you start talking about other skis available, then it's more complicated also. We have pages and pages devoted to the topic.
Unless the Ac30 has changed tremendously, I didn't find it demanding at all. In fact, I would say I found it a ski I could recommend to just about anybody. Intermediate to advanced, they all can get something out of it.
It really was an all around good ski. You could not go wrong, particuarly in the west with that ski. I do agree it had little personality, though that's it's personality.
It is cap construction. It has a different feel to it. Knock them together on the chairlift and they sound like two garbage cans banging together.
Is that bad? No. I actually was surprised by some of the snow feedback from that ski. It's a very decent ski.
The Kastle will have a different feel since it's a laminate ski, and amongst the top in construction. There are subtletys in that ski you just won't get in the Ac30. It has a great tail if you want to push it, and if not it doesn't punish you. There's a feel and feedback from the ski that is smooth, subtle, and addictive. There's a reason a lot of people will only ski laminate skis, and a reason people have written pages about the Kastle.
The upshot is you won't be sorry you bought the Ac30, or you'll be glad you bought the Kastle every time you ski it.
As long as you're ok with the price and can forget about it after you buy it.
If it's a toss up, to most of us I think, the answer's pretty obvious. The white one!