Maybe,
I loaded one round with a primer only and since the bullet velocity was 0 at the muzzle it was not accurate at all.
In rifle rounds there is the issue of barrel harmonics where a small change in velocity can affect accuracy, I would assume you would see the same thing in pistols as well.
For whatever reason I can say from testing that any one of my pistols might shoot a certain bullet/powder combo better at say 1030fps or better at 1060fps or better at 1000fps,
so for example a .2gr difference in powder charge (or an OAL change) might make a difference.
So slower or faster is not always better it is just a matter of finding what
your gun likes.
A load with powder X and bullet a at say 1050fps might shoot better than a load with powder Y and bullet A also at 1050fps.
A load with powder X and bullet A with an OAL of say 1.10 might shoot better than a load with powder X and bullet A with an OAL of 1.08 with the powder charge adjusted to give the same velocity.
Way to many variables IMO to just say velocity makes a difference assuming we are talking about reasonable velocities for the caliber.