It's obviously subjective as to who likes what IP the most. I think it is important to look at it from a business perspective.
Where as I really enjoyed the first How to Train your Dragon movie (haven't seen the sequel yet), I don't remember it moving much merch off the toy store floor. Same for Kung Fu Panda. That franchise is 3 movies deep, but is still not something I see kids wearing on their shirts, or clothes sections at target, etc... Trolls on the other hand was everywhere after it came out. Clothes, toys,
school supplies, even the soundtrack. It had big name voices in it and it appealed to both genders as well as parents who grew up familiar with trolls. I honestly expected to hate the movie, and I actually enjoyed it. It's no classic by any means, but it is upbeat, fun, and fairly quirky. From a merch perspective, I think Trolls wins hand down.
Then there is theming, How to Train your Dragon is fantasy with a heavy slant on a viking setting and .... fantastic beasts. So while the setting is different, the characterization may be a little too close to what they already have over in their new Potter world. Trolls and Kung Fu Panda both offer unique theming options. Panda gives you an exotic local while Trolls lets you play with perspective, crazy colors, glitter, etc... Both offer good selections for food theming, which Universal has shown a huge interest in. On one hand you have a character who likes nothing more to eat and on the other you have.... some odd creature that craps cupcakes and supposedly trolls are so delicious that they cure all depression. I gotta be honest. If I could eat a troll, I probably would. Can Panda be marketed as strongly towards girls as Trolls? I think that is the major question here. Also, as mentioned before, Panda is already 3 movies deep. How long are the legs on that franchise? Trolls just got started and was a huge financial success for them.
I left Shrek completely out of this as it just doesn't seem to have legs on it anymore, and the last thing Universal will want to do is open a whole land based on a 20 year old property. Then again... maybe that is what he was puzzled by...lol.