Ball carry makes them do everything better. Or that is how i see it.
Turn quicker.....agility
Run with the ball quicker.....vision
They end up hitting the holes quicker and cut more often, because they created more space to begin with. To me that is a combo of both or i would call it agility.
And use experience and play familarity as vision per say. But really i see them as all boosts. But for fun i see some patterns unfold similar to nfl backs.
For a bruiser i like STR and BT. I call it a one cut back. Hittin the hole and maybe making one cut, but is more likely to BT and drag defenders.
Overall speed helps with avoiding defenders by forcing them to take bad angles. Increasing another chance to cut again. IMO
And for a Barry Sanders i like high everything maybe not so much STG or BT, but good or great, because he was great.
And the Emmitts with high carry and BT, but lower SPD or STR.
I like carry for fumble too. It seems to put backs at good ball protective angles when taking a big hit at high speeds. Purely hypothetical, but look at i think Nestor on IRN in 75. Thats alot of fumbles that could be the roll or experience.
But i think my team has a plus 10 fumble ratio in 75. I think we lost one or two and opponents have lost like a dozen or so. Its like deflate gate, but problay just luck.
Even my converted TE in mfn 1 who is a vet fumbles alot in comparison to my vet RB1 with elite score everywhere who i work alot more too.
I see the difference being the ex TEs lower STG, Carry, and FUM is is a C grade at best. And it shows in like three times as many fumbles.
Maybe its all dictated by the FUM rating, but much more is at play.