Because your wife would be possibly using this rifle for moose, I was going to choose the 7mm-08 based on heavier bullets. However, I looked up ammo and seems like most of it is 139/140 grain! Norma makes a 156gr Oryx 7mm-08. If you will be shooting 140-class bullets, I think you may as well use a 6.5mm with high BC bullets; it will actually have the same or more energy at the animal. Based on wide selection of factory ammo, the 6.5 Creedmoor is the friendliest option. If you plan to reload, I would use the 6.5x55 since you can stoke it a bit hotter (6.5x55 factory ammo is low pressure due to SAAMI specs). If only deer-sized game were on the menu, I would actually drop down to a 6mm of some kind. The 6.5 and 7mm are a compromise; more than you need for deer and on the small side for moose and elk. But they'll all work, no doubt!