Have been to both, though a little while ago. I prefered Artist's Point. I am a pretty adventourous eater, but I just didn't like the combinations at Jiko. I really did not enjoy my entree. I thought, well I only have to eat the bits I like, bit it didn't really work out. Though looking at a recent menu, I think I would probably do a lot better now. The main thing though was the fact that our server was atrocious. She really was not very attentive at all. Which was night and day to our Artist's Point server, Pok.
Having said that I would be interested to try Jiko again, but probably only if I was staying at AKL. I have enough trouble narrowing my dining choices as it is, without adding resort places too.
I think you would have a great meal at either. Perhaps you could print out a menu for each and hand it around your group, get an idea of what they would like to eat. If you don't tell them which is which, you might get a better impartial view. They are both very atmospheric restaurants, although you will find a few kids, they do both have a more grown up feel.
Enjoy.