Recently i have been thinking about starting to play the belgrade gambit (1.e4 e4 2.Nf3 Nc6 3.Nc3 Nf6 4.d4 exd4 5.Nd5!? is one move order, but the gambit soundness is not the main topic here) of the four knights, and i was wondering about what might be the best move order to reach it. 

Practically speaking, i am undecided between 2.Nc3 and 2.Nf3. 

My understanding is that 2.Nc3 has the added bonus of giving white extra ideas against the philidor-like 2...d6, such as an early f4 which might prove quite challenging for black. 2.Nf3 instead allows black to play a regular philidor. The petroff is avoided with both move orders. Other that this i really don't know.

Is there anybody out there who has experience in the vienna/4Ks and knows something about the various sidelines? Does black have some extra options against the 2.Nc3 move order? Or it is really just a matter of tastes? 

Thanks in advance!

I'm not sure it makes much difference, except as you say that the Vienna move-order gives you some flexibility, by allowing f4 against some black passive set-ups.

I noticed 2.Nc3 g6 is playable though, but I doubt you'll meet it very often

2.Nf3 I think is best as that virtually forces Nc6 which you'll get most of the time. maybe you'll get some 2...d6 games though. Then simply 3.Nc3 when Nf6 is the best. There are other moves but they are trickier to play for Black than White. You can also sidestep any Petroffs this way.

Thanks for the information! Avoiding the not so uncommon Philidor probably outweights the disadvantage of allowing this rare variation...but as you say i guess that the two move orders are more or less equivalent, thanks.

Anthony, the petroff is sidestepped anyway regardless of the move order. I don't think that Nf3 is more forcing at all since as i said it gives white a sound extra option with 2...d6 which is probably much commoner than black deviations against 2.Nc3. So for now i an quite inclined to go with 2.Nc3. Thanks anyway for posting!