I think that 5. ... Nxd5 by black is wrong (much better is 5. ... Na5). So white should never have the chance to play this variation. Even if 5. ... Nxd5 is played the opening book I trust recommends 6. d4 as a much better move for white than Nxf7. So the main line indicated in the opening comment is wrong from both black's and white's perspective. This line should simply never occur.
NM Dan Heisman after exhaustive analysis confirmed by GM Larry Kaufman relying on Komodo analyzed that position as equal. However, as IM Phren has pointed out these pros and I missed---6.d4 Nxd4! 7.c3 b5 8.Bxd5 Qxd5 9.f3! What Heisman and Kaufman should have considered was to leave the piece en prise and just take away the resource Qxg2.
On 9. 0-0....it never hurts to castle....safety first !....
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