They both work, but I would recommend changing Bullet Punch over to Meteor Mash since it allows Metagross to deliver more damage. Metagross should be fairly bulky enough to take a few hits anyway, and the switch-in Groudon will get KO by combo of Meteor Mash and Explosion. The second move set you gave also does fairly decent job of eliminating those weak Psychic-types, and Choice Scarf trick can ruin some of the things that likes to switch-in to Metagross such as Groudon, Kyogre, Forretress, Skarmory, and etc.