"Accuracy" is really the end result of a number of different influences and variables coming together. Although ammunition plays a part, it's a small part in comparison to some of the others.
That projectile you launch has some characteristics. Length, Sectional Density, Weight, Ballistic Coefficient, etc. Provided that each of these are the same and they're fired under exactly the same conditions and at the same velocity, their trajectories will be the same - in other words, their points of impact will be the same. If the velocity of one of those projectiles is lower than another, it will theoretically strike lower on your target. Maybe not enough for you to notice without a caliper, but lower, nonetheless.
So, the closer your rounds are in velocity, the more consistent and predictable they'll become. There is no "gold standard" in terms of extreme spread or standard deviation, only that "less is better."
However, it's important to note that you can have the best ammunition made and still miss the target if your fundamentals aren't up to snuff. On the other hand, sound fundamentals can easily mitigate the variations in your ammunition under reasonable hunting conditions.