I have had both.
The problem here is that we do not have the demand for the Hm2 so the ammo we get is mostly old.
I would run with the Hmr for accuracy and hitting power.
The CZ hm2 I had was really accurate but the ammo was pretty crappy at best. When I could find the Eley stuff, it would one hole at 50yds and do 1/4 inch at 100 with an 18X scope.
I have had more frustration than than anything else regarding the Hm2 and whilst I love the way it stops possum and any other small critter it has come across, the logical choice goes with it's bigger brother.