I use the Aqua Zamp with the Low Profile Raindome. I really like it and my panther usually enjoys the rain effect. His favorite spot is right under the dome and he often "stands up" on his hind legs and drinks the drops that collect on the screen under the dome.
I have not used the Mistking, but I've heard both systems are pretty comparable. We went with the AZ because:
1. Heard nothing but good things about Kevin's customer service and it's true. He is great!
2. We liked that it's made in the USA.
3. We are local to Kevin and were able to pick it up in person, thus saving on shipping costs.
4. He was running a sale which he does from time to time.
Whichever system you get, I highly recommend a Raindome since I think it provides a more natural effect than just mist. *I know you are considering a new cage too. A Raindome does take up a fair amount of cage top real-estate. Our Forever cage is a bit crammed with the Raindome, UVB, and basking lights. Just something for you to consider since you are trying to decide on a cage size too. If you wanted a Raindome, it can be done with the Forever cage, but you'd have more space to work with on the Palace (or 24x24x48).