I'm planning to burn a copy of The Thief for my 4-year-old cousins for Chritsmas, and personally, I think the best choice would be the Princess cut, and for several reasons:
1. It's a finished film. My cousins won't want to watch something that's not finished. At least until they're older. BTW, it was easy to notice the transition from Williams animation to Calvert animation, but I was able to cope with it, and so will they.
2. The story makes more sense. The love tension between Tack and YumYum helps brighten up the story, because with all the animation cut from the Thief stealing the balls and the One-eye sequences, those won't be enough to interest my cousins.
3. It's a reasonable length. Even for me, the Recobbled Cut seemed to drag a bit. The same reason above helps make the movie go faster.
4. The music and the songs. I actually like the music in the Princess cut better than in the Original cut. And the songs, although uninspiring, will appeal to my cousins, who are growing up with those oh-so Disney classics.
Now I haven't seen the Workprint yet, but I did enjoy the Recobbled Cut. And I'd like to see it the way it was originally intended. But to me, the Princess cut is a much more kid-friendly adaptation, and I deem it the best choice to make for my cousins this Christmas. Maybe later on, I'll burn them the Recobbled Cut...
As for Arabian Knight, that's a different story. I have yet to see it, but judging from what I've heard, it's probably not going to be pretty. I'm getting it from Garrett himself, paid him the money, and hopefully I'll get it in a few weeks...