I don't know the theory on who is better and such, but it always seemed to me the philidor gave white small but somewhat permanent edge.  Black gives the impression of being very solid (I guess that's what the opening is known for) but I'm always happy to see it played against me.

Somewhat the same with the Ruy exchange.  White has a small edge, but it feels rather permanent... in these cases though I'm usually fearful of the super complex closed ruy in which I have very little experience.

Pfren is right, you gave this line twice:

After 6.Nc3 there's no reason black can't take your knight on d4.

Yes, I guess I was lucky there. My immediate instinct after black's weird 8...Qf6 is to establish what would be a double Knight outpost with 9.Nd5 though black could reply with g6

The two other moves I've in mind is to finish my (postponed) development with Bf4, which I'd prefer, or to castle, but that seems passive and needless at this time. As long as black is screwing around and I'm developing... 

6.Nc3 is game over man.

with black's queen retreating back to d8 I'm afforded a bit of breathing room and I'm thinking 10.Qe2 or Qd2, 0-0 or Bf4

I play this all the time as white.

This is an improvement for black from the line you posted, so I think white needs to find a different 6th move.

Yes, you're right, but that's not the move black made, and after 9. Nd5Qd8  I decided on 10.Qd2 to prevent a check on my king. Ooh why is it all highlighted. 

Thanks for all the suggestions everyone.

I'd say it's bizarre!

The problem with all this is that since 6.Nc3 drops a piece, the remaining moves are irrelevant.

Actually I didn't in this game - there are still two knights. Irrelevant in what way?

Because you want to find the best moves for both sides when you analyze or at least ones that aren't bad.

You would probably learn a lot by looking at database games with 4...c5 where weaker White players lost to strong Black players.

Am I to understand this is a game which is going on now?

Asking advice of any kind - even on moves already played -  on an ongoing game is cheating, you do understand that, right?

No this is one I played last week but abandoned.  I'm trying to establish what the line is and whether I did it right, because the ones Graham Burgess gives for the Philidor in his 'Mammoth Book of Chess' (Robinson, 2000) didn't tell me if my play was wrong...

You see I don't memorise openings, I don't have an eidetic memory- I just try and stick to opening principles, because if my opponent is going to use a particular opeening, I'll usually bugger it up by not playing along with the moves your 'supposed' to move like some chessic jigsaw.