G'day All

I have a question on what makes the optimal Running Back, but this I dont mean who is better out of Adrian Peterson, Chris Johnson and Roy Helu  but what a team would prefer from a Running Back.

When I look at HIghtowers stats tonight, he has 9 Carries for 56 yards, which looks great, but then you see he had a 37 yard Gain for a TD (which also is great) but the downside of this is that he then had 8 carries for 19 yards.  This got me thinking.'

Would you prefer to have a Running Back that had a true 5 yard a carry average, as in, generally (not always obviously as that would be impossible) the guys makes between 4-6 yards on every play by moving the pile and helping set up plenty of 2nd and manageable situations.

Or would you prefer a game similar to Hightowers example tonight, where he has a couple of long bursts, but still averages out at 5 yards a carry, meaning there were 2 or 3 1st down generating field position changing great plays but a number of runs that left us in 2nd or 3rd and long situations,basically wasted plays.

Is the big play threat enough of a counterweight to all the dead plays, particularly if you are a bit shaky at the QB position.

I do not know the answer to this question, I can see the benefit in both, and I suppose the optimal is to have 2 backs in a tandem who provide both threats, but for the sake of this thougt exercise imagine you just have a feature back and a 3rd down back....  Which style would you choose and why