Main things to consider would be....
- towball weight...KK is pretty heavy and I would sssume AS is the same being they are very similar in design. I've not looked at the CC myself, but I'd be getting real life figures from owners on all 3 to get a true comparison.
- sleeping area....are you planning on the kids sleeping on the hard floor or an extra room? We have 2 kids that sleep on the hard floor of our KK (14yr old is same size as an adult and a 10 yr old), they take up almost the entire floor just about which is fine for a weekend, not great for longer periods. The extra room on the back is great space wise but only good for 2 kids for extended time IMHO, unless they like a tight fit crammed in like sardines, so one would have to go on the hard floor. You need to look at what the other trailers have, i've not looked st their options to know if they are any better or not.
- storage....for long trips in our KK there is enough room to store clothes for 2 adults under the bed but not 4 people, our kids clothes go in the back of my 4wd in bags. Weekend trips away we fit everyone's clothes under the bed in the draw easily, but when you need enough clothes for an extended period and both hot and cold climates, you need to look at where they'll all go. Taie a good look at the 3 and realistically work out what can fit where.
- extra storage.... you'll likely need to pack 5 camp chairs and a table in somewhere, where will they go? Getting stuff off and packing back onto the roof rack of the vehicle becomes a pain to do, we have a table that slides under the bed draw (fits 4 people only) and I have a storage box I added to the top of the front boxes on our KK to take 4 chairs, a small ladder I use to put the awning up (makes life easier for the high middle section), and also has a levelling ramp in it. You need to consider where will that gear go in all the campers. Where will the kids beds go?....mattresses and sleeping bags, pillows etc?
I probably come off sounding abit negative to the KK, but the trailer has been fantastic for our family of 4 the past 7 years we've had it. Owning one means I can give my true option of what they are like, but reckon AS would be identical as the 2 are very similar trailers, and no experience with a CC.
I'd suggest you work out one day what you think you'll take away with you on a year long trip for the family of 5 (you'll be surprised how much room 5 peoples clothes takes up for example), then try and work out where it'll go in the camper and vehicle. Having done a 6 week touring trip in a Landcruiser wagon, I'm happier these days I have a dual cab 79 series with a canopy on the back, because there's so much more room to put stuff in the back. Putting stuff on the roofrack each day gets old fast as it's time consuming tieing it down or strapping up the roofrack bag...sounds negative again I know, but having done this before I know I got sick of doing it, and just trying to give you things to think about.
Good luck with your decision, wish it was my family undertaking such a trip