user8291: As title above, why is the Advance Variation in these recent years considered strong vs the Caro-Kann, especially owing to White's early space advantage in the center, but not vs the Scandinavian? In other words, the Advance Variation (especially the so-called Short System, with Nf3, Be2 etc.) is considered a strong way to fight the Caro-Kann. On the other side, after 1.e4 d5, the move 2.e5 is considered weak (or even a mistake) because Black can develop his Bishop to f5, obtaining a "better" version of the Advance French. But isn't the structure with ...Bf5 then very similar to the Advance Caro-Kann (which is considered strong)? 

user7297: Against a white d4-e5 pawn formation, Black wants to play c5 (see e.g. the French opening). In the Caro-Kann, that will cost two moves (c7-c6-c5), while in the Scandinavian, it's only one move since the pawn is still on c7. That's one tempo, and as @Qudit notes in the comments, in the main line Scandinavian White usually wins a tempo by chasing the black queen around. So it's actually a difference of two tempi, which makes a huge difference, as is often the case in (semi-)open games.

8291: <p>As title above, why is the Advance Variation in these recent years considered strong vs the Caro-Kann, especially owing to White's early space advantage in the center, but <strong>not vs the Scandinavian?</strong> In other words, the Advance Variation (especially the so-called Short System, with Nf3, Be2 etc.) is considered a strong way to fight the Caro-Kann. On the other side, after 1.e4 d5, the move 2.e5 is considered weak (or even a mistake) because Black can develop his Bishop to f5, obtaining a "better" version of the Advance French. But isn't the structure with ...Bf5 then very similar to the Advance Caro-Kann (which is considered strong)? </p>
 7297: <p>Against a white d4-e5 pawn formation, Black wants to play c5 (see e.g. the French opening). In the Caro-Kann, that will cost two moves (c7-c6-c5), while in the Scandinavian, it's only one move since the pawn is still on c7. That's one tempo, and as @Qudit notes in the comments, in the main line Scandinavian White usually <em>wins</em> a tempo by chasing the black queen around. So it's actually a difference of <em>two</em> tempi, which makes a huge difference, as is often the case in (semi-)open games.</p>
