The only way Emmitt was able to take rushing title was to play 4 years after he was washed up. He averaged 750 yards a year for 4 years to do it. If quit when he was washed up, he would have about 3000 fewer yards.
Emmitt's average was 4.2 per behind the best line in the NFL. That is good enough for about 170th all time. He was handed 3 of them and fell down for 1.2 per. Barry was handed -2 per and was able to end up with a 5 per average.
To me, that makes Barry 5.8 yards per carry better than Emmitt.
However I would take a running game like Dallas' over a running game like Detroit's. Obviously because of the rings. Not as obviously because when you have a breakaway back, you have feast or famine.
I look at AP of the Vikings for an example. Before last year, he was averaging about a 20+ yard run per game and about a 40+ run every other game. If he averaged about 24 carries and 100 yards a game, he would have 40+% of his yards in 1.5 carries a game. Leaving an average of less than 60 yards on 22.5 carries for the rest of the time.
The problem is, a few good runs a game and the rest being under 2.66 per per makes it hard to sustain drives, wear down defenses and control the clock. A couple of big gains and the rest are 3 and out. And with a break away back, you have to keep feeding him to get your moneys worth out of him. He needs that 20 plus carries to get the production. So you are stuck with the running game, waiting for that 6% chance that this is the one he breaks.
I want to go out like my Grandpa did. Peacefully in his sleep.
Not screaming in terror like his passengers.