Forward arrow: I want you to stand here, exactly, whenever we have the ball.
Forward runs often: Use your judgment. If you feel it would be advantageous to go further forward than your current positioning, feel free to do so.
Forward arrow + forward runs: I want you to go to at least this spot whenever we have the ball. Use your judgment about making runs beyond that location.
Take a look at some of isuckatfm's work on
Page 5 of Several game and football questions.
I'm particularly impressed with
This screen shot. Notice where his fullbacks have gotten to. They don't have arrows forward, they just have "forward runs" .. presumably, if the opposition were in a more threatening configuration, they might have decided it was less advantageous to get forward.
I'm becoming convinced that "forward runs" are a bit better than forward arrows. For my next tactical experimentation, anyways.