In Caro-Kann Defense, what are the differences between 3. Nc3 and 3. Nd2? After 1. e4 c6 2. d4 d5, what are the differences between 3. Nc3 and 3. Nd2?

It seems 3. Nc3 is more popular, though after 3. ... dxe4, I failed to see the difference.
3.Nc3 allows White to play the Two Knights Attack with 2.Nf3. It does block the c-pawn, though, so Black can play 3...g6, the Gurgenidze System, because White cannot protect the d-pawn with the c-pawn.

There is also the rarely played Gurgenidze Counter Attack 3...b5. A very dubious line that can be stopped easily with a3.

3.Nd2 tries to avoid these lines, but it makes the Two Knights Attack impossible, a line that is very popular nowadays. It also blocks the view of White's dark-squared bishop, so Black can develop their kingside knight to h6 if they want.