How does the comparator make it different?
The comparator measures base to a point on the bullet ogive. This avoids measuring against the tip, which may be slightly deformed, and so change the measurement. It is useful when you are loading lead-tip bullets.
Or would a runout tool make much difference for hunting cartridges?
It makes a difference if it makes a difference for you.
Runout is a measurement that tells you how
1. far off center your decapping die assembly is in the sizing die
2. if your bullet seating stem doesn't match your bullet profile
Some people get OCD about runout, others never measure runout, just size with no decappig pin assembly, and make sure the bullet seating stem fits the bullet ogive.