I would go with .22mag ammo is much cheaper, as well as rifles. I've not shot a .22mag before, but I've heard good things about them and did a quite a bit of research when deciding between it and .17HMR. Marlin's are great guns too so good choice. Honestly I would go with .17HMR over .22mag though. Much flatter trajectory, better groups, farther range. Depends on what you want to hunt though. That's my two cents.