Tough call. I'd be pretty heartbroken to lose either my Model 70 .30-06 (bought from a friend, whose dad bought it the first year they came out, and the rifle I killed my first big game animal with), or the Mark X .375 H&H I used in Africa.
But since I have other rifles that can do the same jobs (or at least could easily buy equally serviceable ones out of the box), I'd go with my 10-year-old Schnees Hunters. Rifles don't need to be broken in. Boots do.
