Japan vs New Zealand?

I just got back from Japan and fell in love with the country. I was thinking of going back since I have enough miles saved up however I’ve also dreamed of going to New Zealand and I also have enough miles for that as well. I just can’t decide. I loved Japan and know I could get around easy and enjoy myself on a solo trip without a car. New Zealand is really enticing as well however I’d prefer not to drive on my own. I have about 15 days I was planning on going. Any opinions would would be appreciated.