It is going to depend on the individual revolver. You will have to test.

"Working up" a load means you fit the round to your gun. There will be a point between the min and max loads where the bullet and powder just "fit" right. It may not be a big difference but it will be here.

Concerning the reputation of the 44 Special accuracy, one thing I noticed about the fixed sight versions of S&W and Colt revolvers is that the sights are well regulated. In other words, they hit right at the point of aim. A lot of fixed sight guns do not. I guess you could call that accuracy. If you pick up a 38 Special and miss tin cans at 20 yards and then make good hits with a 44 Special, then you might say the 44 Special was more accurate.