I quite like both worlds equally, but if I had to choose, I would say that I like Krok more because I do like lizards. Also, I think I like Krok more because it is the main story line, whereas Wysteria is a side world. It would be wonderful if they expanded Wysteria. I've always been curious as to what spells those schools used, so I would love to see what kind of spells they have in store(:
Though I can't even get past the first boss Wysteria is my favorite so far. I even have a friend who completed it. He also told me (My friends tell me so much spoiler stuff that helps me) that you get the A+ Student Badge, plus KT had way to many dungeons.