Harry potter wizards collection or the wizarding world of Harry potter?
I say that you should wait until you see what souvenirs the Wizarding World has before you make a decision. If you already have all eight dvds, it may not be a good idea to buy the wizards collection now. The price in the US at least averages about $43 a movie, not including the bonus movies (about $29 including). The price may come down eventually, so you should wait to see if the price comes down or if they have a sweepstakes or something where you may be able to win one. Personally, the bonus materials to me aren't that interesting (except for deleted scenes), so the price is just too high for something that I already have. In the Wizarding World, you don't just get the movies, you get to experience the world. You can try butterbeer, pumpkin juice, chocolate frogs, and other things in the Harry Potter universe. If you want an idea of the sort of souvenirs the Wizarding World has, you can see a shop on the Universal Studio Orlandos website.
What to buy at the Wizarding World of Harry Potter?
I would really wait until you get there, examine all the stuff, and then decide. The wands are a piece of plastic. I think they are the biggest, silliest money-waster thing there. But people go crazy for them. Think about what you will do with it when you get home. It's not exactly usable, and it's not especially attractive for display. As you go through the shops, think about what you will do with it - how much use will you get out of it? Like people with the little time-turner keychains - they put it on their keys, and that reminds them just a little everyday of the fun they had there. I still say they are overpriced, but that makes more sense to me. Spend your money wisely. And on the candy/food, just pick whatever appeals to you when you see it! The beans and the frogs are right out of the books of course, but there's lots of little fun things to try. For Butterbeer, I think frozen.