First of all....CONGRATS!!! That's great!
Personally, it would depend on what is included. If it's all expenses paid, except for souvenirs and personal purchases of course, then I'd be jumpin' all over Japan. Given that it's so expensive there I think that you'd be getting most out of your winnings if you went there. (If it's all expenses paid, of course).
A little biased , too, in that when I collected stamps as a kid, I was always intrigued by the Japanese stamps and have always wanted to go there...someday...as a result.
But whatever you decide, I'm sure it will be awesome.
Can't beat a freebie!
Looking forward to hearing about it, if you care to share.
Bon voyage and cheers,