In both the Smith-Morra (accepted) and Goring gambit lines, white offers a pawn on c3. If Black takes the pawn on c3, White can play Bc4, offering a second pawn in exchange for rapid development with highly active bishops.
Although neither line is winning for White, according to Stockfish, the extra pawn sacrifice is significantly more viable in the Goring (-0.4) than the Smith-Morra line (-1.23). Why is this?
[Title "Goring Gambit with extra pawn sacrifice"] [FEN ""] 1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. c3 dxc3 5. Bc4
[Title "Smith-Morra Gambit with extra pawn sacrifice"] [FEN ""] 1. e4 c5 2. d4 cxd4 3. c3 dxc3 4. Bc4