Less demands for ammo (and probably less supply)
Ability to shoot for anything that is rimfire restricted - varmint hunting is restricted in some states (especially at night)
most likely none of this matters to you... so it's just another toy
And comparing it to the 223 doesn't yield as much of a difference as comparing it to other rimfires.
Ex: It's about 60% more energy than the HMR and carries the effective range out to 200-225