As a general “rule”, I have read that pawn captures toward the center should be preferred. I have found 2 different positions which look similar but the best way for Black to recapture with the pawn is different.

[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"]

1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. Bb5 Bc5 5. Bxc6 bxc6!?

In the variation above, Black captures toward the center but Stockfish labels it as an inaccuracy and suggests capturing with the d-pawn instead. The advantage goes from 0 to around +0.6.

[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"]

1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. Qe2 Bc5 5. Bxc6 dxc6!?

In the variation above, Black does not capture toward the center this time. But Stockfish still labels is as an inaccuracy and suggests capturing with the b-pawn instead. The advantage goes from 0 to around +0.8.

The positions look very similar to me. Why does Stockfish recommend recapturing in different ways in these positions?

As a general “rule”, I have read that pawn captures toward the center should be preferred. I have found 2 different positions which look similar but the best way for Black to recapture with the pawn is different.

[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"]
[Title "Spanish Variation 1"]
[StartFlipped "1"]

1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. Bb5 Bc5 5. Bxc6 bxc6!?

In the variation above, Black captures toward the center but Stockfish labels it as an inaccuracy and suggests capturing with the d-pawn instead. The advantage goes from 0 to around +0.6.

[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"]
[Title "Spanish Variation 2"]
[StartFlipped "1"]

1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. Qe2 Bc5 5. Bxc6 dxc6!?

In the second variation, Black does not capture toward the center this time. But Stockfish still labels is as an inaccuracy and suggests capturing with the b-pawn instead. The advantage goes from 0 to around +0.8.

The positions look very similar to me. Why does Stockfish recommend recapturing in different ways in these positions?