Caro-Kann 3...Bf5 or 3...c5 ?

Can someone explain me the difference between those 2 moves ? 

Is one better than the other ?

Thanks

Depends on what whites third move is.

I've only just started playing the Caro-Kann, but I'm adopting 3...c5 against the Advance variation, because it seems much simpler to play. Basically you've got a French Advance a move down, but that's actually good because you haven't blocked in your white-squared bishop with e6 and will be able to develop it in due course to f5 or g4. As the Advance vaiation of the French is OK for Black anyway (and I'm a French player, too) this is very attractive to me. The early Bf5 on the other hand is more committal, and you run into some dangerous ideas like 4.h4, intending to harrass your bishop with g4, which can lead to sharp play. 

I prefer 3...Bf5

With 3...c5, white can nudge black into playing a French Defense type of game, like so:

Now black is down a pawn, and has to fight to win it back. Black also was forced to play ...e6, shutting in his queen bishop, which kind of defeats the purpose of choosing 1...c6 over 1...e6, in the first place.

The position is entirely playable, of course. But it's definitely less "Caro-Kann" and more "French", at this point.

4...e6 would be better than Nc6.

I'd prefer 3...c5 over Bf5, there are plenty of good variations against Bf5 for white: most strong of them are 4. Nf3 -> 5. Be2 setup, and 4. h4 -> 5.c4

I've shifted away from Bf5 in favor of c5. I like the resulting positions better, they more reliably lead to imbalances in the pawn structure that allow me to play for the win. Both moves are perfectly sound though, and played at the highest levels.

If you really want to explore the differences, I recommend checking out the Caro-Kann Cutthroats' vote chess games. We've played quite a few games against the Caro advance, and we've pretty much alternated between Bf5 and c5. In completed vote chess games, you can see the discussion for every move by clicking on the moves under the "archive" tab - and our group has the best discussions I've seen in any vote chess games.

If you like playing the Caro-Kann, you're of course welcome to join the group too.

It's a matter of taste, for sure.

Though, after 3...Bf5, black has some good options against those variations, too:

Against Nf3 + Be2:

Against h4 + c4: