Like to the point where it seems you are watching a different game.
Estime and Diggs have the same exact number of carries running behind the same OL. Estime has 135 more yards, his avg is 5.7 to 4.6, his long is 46 to 33, his rushing TDs are 9 to 1, and his receptions are 6 for 96 to 4 for 70. It's not even close and I'll say this (again I like Diggs, as I said I think he'll play on Sundays) if Estime hadn't had those 2 or 3 games with fumbles early on, he would be the clear cut #1 right now and would probably already be over 1,000 yards.
The time when these two look the closest to each other, is when the plays are blocked up nicely. Diggs has the better lateral movement as the significantly smaller back and when you block Diggs to the second level I'd say he's right on par with Estime in open field effectiveness, just for different reasons.
When the plays are not blocked up well is when Estime separates himself...he is much better at creating yardage that isn't there. Now if you're talking about plays that are blown up in the backfield where defenders arrive just at/after the RB gets the ball, yeah Diggs has better initial quickness to maybe get back to LOS scrimmage instead of taking the 1-2 yard loss. But if you give both these guys clean handoffs where they can approach LOS unharassed,, but OL hasn't blocked up running lanes well Estime has shown far greater ability, like it's not even close, at creating yardage, using vision to find alt running lanes and even being nimble and getting small through tight spaces.
I like both of these guys, but there is a reason Diggs was doing nothing vs Navy while Estime was having success, Navy has a good run D and our OL was not blocking them up well. One back was still able to find success while the other was completely nullified...the difference here is quite obvious.