with French you will be able to grasp the other Romance languages such as Spanish, Italian, and Portuguese much more easily, it has the benefit of 'making other languages easier' in the long run.
This is useful if you are just 'doing it for fun' mostly.
German however is more useful in the market place as a whole, since Germany is the 3rd(?) richest nation on the Earth, and thus, has a market to match.
It is difficult however, yet worth while.
This is useful for more professional needs, but more difficult for 'just for fun learning'.
It depends on your motives, and your future wants. Either one is worth while.