I would say a cross between hiragana and kanji. There are over 2000 kanji that should be learned for every day life, so that you can read things like newspapers. But if you just learned hiragana, it's passable and would seem childish, but you will be understood. Some words and parts of words can't be written in kanji, which is why I believe both kanji and hiragana are used just as much as each other. That's how I feel, though. There may be other opinions.