Petroff or the Philidor

If you had to choose

Which one and why? 

Philidor

Easy!

Petroff!

Reason is two-fold.

1) The sounder of the two (objectively speaking)

2) Metcalf personally, it's an extremely easy choice as the only two openings I have played over the board as Black against 1.e4 in the last 8 years have been 1...e6 and 1...e5, and against 2.Nf3 after 1.e4 e5, 100% of the time I responded 2...Nf6, so a VERY EASY choice for me.

Way less theory.

If your main prerogative is less theory, play the Borg (1.e4 g5). Poor excuse to choose the Philidor over the Petroff.

The Petroff is fine. I wasn't suggesting that the Philidor was better. I was referring to the overall amount of theory needed to play the Petroff as opposed to the Philidor. Particularly, White's second move alternatives.

This is why I generally don't answer questions like this because I end up having to write paragraphs explaining what my reasons are.

Chess is a big ocean. There is room to swim for every one.

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?".

Petroff, because your opponents will eventually find very aggressive lines versus your Philidor/Lion and all your study there will be questionable, I have played both

I would choose the Philidor because it is less symmetrical and more unbalanced.