Stag and bone will last the life of the knife if cared for a little. A bit of mineral oil rubbed in once in a whole won't hurt.
If you go for stag, try to make sure you are getting the real India Sambar stag. It's more dense with no pithy core like alot of deer stag. Really tough stuff.
Bone has a very long history of hard use knives. All the early original Russell Barlows of the mid 1800's has rough saw cut bone for handle scales. They held up well. Case uses the shin bones from Argentine cattle for a dense tough materail. Mt father had a little Case peanut that had brown bone handles that he got in the late 1930's, and it was his daily pocket knife, used for everything. It had a crack in the bone on one side that had developed after more than 40 years of constant use, and it was easily replaced by the good folks at the case factory.
Either on is good, but my own prefference is to stag, I just love the old golden brown hue it gets as it ages.