After the initial moves of the French Defense: Exchange Variation, my opponent played 4.b4+. I followed with 5.Bd2, but after analyzing it, I saw that it is not in the master games opening on chess.com and 5.c3 and 5.Nc3 are considered better moves.

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1. e4 e6 2. Nf3 d5 3. exd5 exd5 4. d4 Bb4+ 5. Bd2

It looks like the most natural move to me, because:

• It forces the bishop away or to take my bishop which I can recapture with my knight, therefore developing it if he decides to take
• c3 looks like a less natural move because although it pushes back the bishop, it prevents my knight from developing on c3 in the future
• Nc3 looks like a less natural move because it pins the knight to the king, and if he takes my knight, he gets my pawns double stacked on the c file, which I always have thought you should try to prevent

So, why the move is weaker?

After the initial moves of the French Defense: Exchange Variation, my opponent played 4.Bb4+. I followed with 5.Bd2, but after analyzing it, I saw that it is not in the master games opening on chess.com and 5.c3 and 5.Nc3 are considered better moves.

[fen ""]
1. e4 e6 2. Nf3 d5 3. exd5 exd5 4. d4 Bb4+ 5. Bd2

It looks like the most natural move to me, because:

• It forces the bishop away or to take my bishop which I can recapture with my knight, therefore developing it if he decides to take
• c3 looks like a less natural move because although it pushes back the bishop, it prevents my knight from developing on c3 in the future
• Nc3 looks like a less natural move because it pins the knight to the king, and if he takes my knight, he gets my pawns double stacked on the c file, which I always have thought you should try to prevent

So, why the move is weaker?