Hi Velo, I was in the same situation & after some similar deliberations I settled on the K2 Juvy (daughter) & the Nordica Ace of Spades (son) for a few reasons. We too have graduated from beginner skis and need something more suited to advanced skiers. We usually ski Mt Rose or Northstar and my kids can ski the back side of Northstar (easy blacks) and like to dabble in the trees there and the frontside parks.
Since the Juvy's will be passed down to my son I chose the Juvy instead of the Missy as I figured the Juvy was more non-gender specific.
I was also looking at the Gotoma's & the Atomic Century's, but they seemed to be more fat powder ski oriented. We demo'd the Juvy's last year during a 12" powder day in March & they were great. Any more snow and yes, the Gotama's probably would have been better :)
The Juvy's do have the rise and are directional twin tips so they should be great in the park & features as well as in the wide spaced trees @ Northstar.
All in all, for a 1 ski quiver I just felt like these were the best all around skis for what my kids like to ski.