Najdorf Bg5 VS Rauzer

I'm trying to understand the positional differences between the Najdorf Bg5 and the Richter-Rauzer.

Particularly, I'd like to focus on white perspective and why the white Q normally goes to Qf3 in the former, and goes to Qd2 in the latter.

Analyzing the database:

Here's the Najdorf, and white now almost always plays f4.

Here's the Rauzer, and white now almost always plays Qd2.

Note that playing viceversa is not only rare, but it scores really badly. So I'd really like to know what difference does it make that black played a6 instead of Nc6.

Second:

White setup in the Najdorf

White setup in the Rauzer.

The only difference is the position of the Queen. Can somebody explain why the white Queen is better placed on d2 against black's different setup?

Thanks in advance.

Note that I didn't ask which opening should I play :)

Well, White does have to keep his d4-knight protected. 

@ AndyClifton: yes thanks: would it be bad for white to exchange the knight?

@ pfren: "only difference" in white's camp, and I'd like to understand it.

Look I know what I'm asking probably to you sounds like a child asking his father why he has to go to work, but I would appreciate if you could drop some hint.

well i dont play either of these lines, but just a few points of note.

The d4 knight need be protected, the exchange would give black the opportunity to easily get in d5 aided by the new c6 pawn. (dont know if its that bad).

often i know the knight goes to d7 in the najdorf, so perhaps we can decide since it is already commited to c6 the setup applying pressure down the d file is a better way of meeting this, as defending with be7, after bxf6 black must recapture with the g pawn otherwise d6 would be hanging. while in najdorf lines they can recapture with a knight keeping their pawn structure in tact and d6 defended.

other than these (probably misinformed/wrong) insights i cant think of too much else. though im sure the moves have a much much deeper theoretical purpose than i can garner from looking at the diagrams.

 

^ thanks.

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