Personally, Philidor. White has fewer choices of different plan, making it easier to learn and I don't have much time to devote to opening study. I know that's not a good objective reason for a preference, but in the world as-we-have-it one must cut one's suit to fit one's cloth. Black keeps White guessing about his broad intentions a little longer too; as in, "Is this going to be a classical Philidor or a Hanham/Lion or even a Mestel-style Philidor Gambit?".
You are sadly mistaken!
In fact, the Philidor can be completely avoided! What if I told you I could force you into a Saemisch Kings Indian or Saemisch-Style position against the old Indian? Yep! Even with the whole theory that 1...d6 is a better move order - try again! There are also many anti-philidor lines in that move order!
After 1.e4 e5, it is the same options for White to avoid the Philidor as it is to avoid the Petroff.
After 1.e4 d6, the following all avoid the Philidor:
2.d4 Nf6 3.Nc3 e5 4.dxe5 dxe5 5.Qxd8+
2.d4 Nf6 3.Nc3 Nbd7 4.f4
2.d4 Nf6 3.Nc3 Nbd7 4.g4
And then there is my favorite:
2.d4 Nf6 3.f3! Where 3...g6 4.c4 Bg7 5.Nc3 is a Saemisch King's Indian and 3...e5 4.d5 can lead again to a saemisch kings indian or an old Indian setup, depending on what Black does with the Bishop.
Hello ThrillerFan, good information and yes the Philidor, the Old KID, and the KID are interrelated. They are sister openings in my opinion. One could make a repertoire out of the Philidor and the Kings Indian against 1.e4 and 1.d4.
Your 4 lines in the 1.e4, d6 move order do look good and correct. But just some thoughts upon further evaluation. I will answer in order
A) the line with Qxd8+. This is the Philidor end game line. Black can protect the pawn on e5 and once the king can move to e7 then black actually has the advantage in this position. You can look at any or every database and you will find almost no games played from this position above about the expert level. It reminds me of the KID end game line which is what allows black to play e5 in the KID to begin with.
B) the two lines with 3...,Nbd7, don't play Nbd7 play e5 with the intention of going into a exchange Philidor. White has to allow it or we reenter the endgame line in line one.
C) the line with 3.f3,... yes it does appear that it leads to a Saemisch Kings Indian. And it is probably in Black's best interest to go there.
Just in case your wondering why 2…d6 is an error.
When White plays Grand Prix Attack, It is a very aggressive King side attack (Flank Attack).
Black best way to survive the attack is be counter attacking in the middle with the moves e6 + d5.
If you play d6, Your D pawn will have moved 2 times because you ideally want pawn on d5 in that position.
So the move d6 is an error because it gives white an extra move.
If you play d6 + e6 + d5, You have played 3 moves.
If you play e6 + d5, You have played only 2 moves.
Thank you. Point taken. But the extra move may not be as big of a hindrance as it seems. I have been playing c6-c5 in the Caro kann for years. Same idea different pawn. I would need to see some definite concrete lines to evaluate farther. The price of an extra move may actually be reasonable:
A) if it immediately removes white from their intended game into a much different style of game. And if they have no intimate understanding of the Gran Prix Attack theory because they thought that they were going to play a Kings Gambit. You of course would have studied it because you are the one with the plans to go there to begin with.
B) The trade off is now white is committed to playing a certain variation of the Sicilian. When if he wished to play a Sicilian by the proper move order could have had a much broader variation of Sicilian to choose from to begin with.