in your opinion

Neither one is "better."

Many lines of the French offer Black a better chance of winning the game, but it also provides Black a better chance of losing the game.

Many Caro-Kann lines are modest attempts to hold the balance,
where Black hopes to exploit a nuanced White mistake.  And yet many lines of the French feature full blooded counter attacks and dynamic unbalanced positions.

Playing the French well probably demands more theoretical
preparation and general chess understanding than the Caro Kann.

Both French and Caro Kann have their owns tastes. It depends upon your style of play.  I've read that overall, the French is more complex and tends to be more of a tactical game, while the Caro-Kann is a solid and positional game.  However, with my games I'm not so sure that's true. 

I play both the French and the Caro-Kann and I'm a big fan of both.

I'd started off with the French and switched to the Caro-Kann, but that was just because of my personal preference after getting familiar with both. Like the others have said, it's a risk/reward factor. You could rank the major replies by black in terms of risk/reward as follows:

1. Sicilian

2. Open game (e5)

3. Pirc/Modern (more risky than e5, but less performance reward imo)

4. French

5. Scandinavian

6. Caro-Kann