I think it is mostly preference once you get to the quality ball head vs Anvil 30.
The differences are really minimal. But the one thing I like is the feel of the inverted ball head and the lever lock. I use the lever to drive the ball head when glassing and shooting.
With a ball head, the knob is not connected to the ball head, so you absolutely need two hands for glass and have to carefully drive the rifle so it doesn't roll over.
One of the best shooters I know, a professional, prefers the 55 over the Anvil.