Depending on your kid's ages - but I love AK no matter what age you are - my Dad and Grandma went with us last year and had to choose, and we took them to AK with our kids - when you add up the safari, Festival of the Lion King, Tough to be a Bug 3D show, walking through the trails and seeing gorillas and tigers, the Dinosaur ride, walking and shopping in Africa, the Pocohontas show, the Jungle Jammin parade, all the characters you can meet (best place for Eeyore and friends!), and just admiring the Tree of Life, you have a full and wonderful day of fun and memories for everyone. My teenagers love MGM for the thrill rides, but they'd still pick Animal Kingdom - the spinning coaster and Dinosaur ride and kali river rapids are thrilling enough, and they'd ride the safari all day if I let them, because it's different every time. No matter what you choose, it's Disney and you'll love it!
However, if you do choose MGM make absolutely sure you're there on a night Fantasmic is playing and DON'T MISS IT!!! That alone is worth the admission.