I use the .451s. I have found that they shave a nice ring. I have not measured the ring, and my estimates are poor.
The real test I am using, is the force needed to get the ball into the cylinder, and to shave that ring. And that force is rather great even with a lever to accomplish it.
I think if I tried the .454s the lever would break off. That has been known to happen.
Now, I may have a cylinder that is just a bit smaller than yours. Or because my gun is new, it may not have worn out to a larger size as yet. Maybe someday it will.
Or they may be selling me balls that are a slight bit larger than actual .451.
If I ever find a .451 that loads too loose, or if I ever see some movement of the seated ball after recoil, then I will consider going to the .454s.