Which is more useful? Japanese or Spanish?

Definitely Spanish! Hahaha LOL do you know why? Because Spanish is the second language spoken in the world. Also Latin America has best beach ever, food and nice people. Take a lesson start learning Spanish!

This depends on your country and your reason to learn them.Spanish is spoken by more people, but again, it depends on you and your background. Which language is more appreciated in your profession and in your country. You can always try learning both at the same time and see how it goes. They are not related so you will not get confused. Also, maybe you will learn which language fits you better.