I have recently read a chess book in Spanish which gave the following line for the Scotch game after black moved 4... Qh4 (don't know the name of it). It is the following line:

 

 

 

 

 

 

The resulting position is drawish, with no advantage for white. But analyzing the moves with the Chessbase engine it gave another combination of moves, derived from white playng 6. Bd2 instead of N1c3. The position for white in this second variation seems better for white to me:

 

 

 

 

 

 

 

I tend to rely on humans rather than on computer engines, but in this case evidence suggest that the engine analysis is better. Is it right or am I missing something? 

Yes, I would rather play the second line, but 8... Kd8 (Fritz 11 gives this move .49 pawns advantage for White) looks better than Nce7 (Fritz 11: White 1.5 pawns advantage).

I personally play the 4...Qh4 variation over the board (called the Steinitz Variation) and use this book as a reference, which I believe to be the latest published word on the topic.  In that book they don't recommend 6...Qxe4+ but rather 6...Bc5.  That sets up 7...Nd4 (after Qe2) if black wants to go that way, or just 7...Nf6 hitting the e-pawn (daring white to play 8. Nc7+ as after Kd8 and Nd4, white is in considerable hot water.

Interesting lines, both.  The chessmaster line looks darn near winning, although black makes some moves I'm not sure I understand... I'm pretty sure Black's play can be improved in that second line. 

Just one comment I mildly object to --  At the end of the first opening you say:

The resulting position is drawish, with no advantage for white.

IMO, It might be drawish for top-flight chess players, but for mortals like you and I, it isn't. White holds a clear advantage in dynamic factors like development, piece activity, open and 1/2 open files, -- but has some clear static disadvantages as well -- down a pawn with an isolated d pawn.  If this is equality it's a tense one  with a lot of competing imbalances. Both players will need to play accurately.

Why doesn't white play this:

Black is one tempo behind and white can castle, and black has doubled pawns 

( is black certain to undouble his pawns later on?)

 

OR is black going to do dxNc6

That isn't so bad for black because he is a pawn up and it only takes one move (Be6 or Bd7) to queenside castle.

Afterall what about 6. Bd2?

And another tip. I also play Scotch as white, I go for this position.

 

 

 

 

 

 

 If you also want to reach this, you may play 1. e4 e5 2. Nc3 Nf6 3. Nf3 Nc6 4. d4 ed 5. Nxd4 and now 5... Qh4 is not possible because of the black knight on f6.