Hey die Marcel,

I started following keyboard-lessons four years ago (I was 14 at that time). I really enjoyed (and still enjoy) playing. Now, however, I really wish I had learned to play piano first. Because if you can play piano, you can play keyboard, but if you can play keyboard, it doesn't mean that you can play piano.
I would choose the piano if I were you, but this is a decision you have to make yourself.

Maurice