Game Design. Its more important to do what you enjoy for a career than the bigger $$$. You will be much happier going to work everyday for all those years when you do what you love. 

Think about it...30-40 years later when you look back on your life you don't want to feel like you settled for a career you didn't enjoy as much compared to a 3D modeling career you could have excelled at because you're really talented and passionate about it.

Oh and 3D modeling does make good money just like Phoenix_Wiight said.

I'd go for the money. A dream is nice until your interests change; then you'll be stuck in a place that doesn't pay as much and doesn't interest you anymore. Money is security- you can branch out and follow your dreams then

Money, it allows you to unlock your dreams.

follow your dreams!!

if it makes you happy then you'll want to do it, and the more you do it the more you'll get ahead of others with no passion for their work, it's a win win :)

Do computer systems engineering.

that way you can get the best of both worlds. You may not get to design 3d models for computer games, but you will get to do modelling of stuff as well as developing of software.

Then once you get experience, you could easily transition into gaming, if the gaming company goes bust you can easily go back to software development.

do game design. You will never be as good as the ones who are doing Computer Science with all their passion.

I want to write a script for a video game. I love writing stories and I am pretty creative. Well actually I dream about certain situation from a 3rd person view. A dream without me in it. Just a story that keeps playing and I am watching. All I have to do is write what I saw.

We should team up then

In Germany you would have a very hard time to find a job as a game designer.

So I'd say go for the option that has the most potential ("money" in this case)