Since you don't have strong preferences, why not go with your parents' preferred choice, whatever that is? Both are great countries to visit, and both will give you more than enough photographic opportunities, be it landscapes or street. And for the end of the year, you might want to consider going to a location with a high chance of snow to get the full winter experience. Though take note that snow is never guarantied with the wonky weather nowadays....
But I agree that photographers should at least make one "pilgrimage" to Japan to check out the photography section of the massive electronics superstores. B&H store in New York should be another "must-see", but I've not been there yet so can't comment more.