I can 100 % agree with Rick.
The reason, why horn isn´t as hard as stag (for example), horn grows with the animal and won´t be lost durign life of the animal. Stag is someway of disposal. A deer, for example, will loose its stag during life a couple of times. It doesn´t grow with the animal so it can be harder than horn.
Horn is pretty soft and smooth, so it needs some attention agains scratches etc. But some of the hornhandles look really nice. I saw some of Faustos (quattromori), which were traditional italian patterns. Beautiful material! But imo it needs a lot of attention.
Wood is imo nearly as bone. It doesn´t need so much attention. The material is pretty tough.
Hope this could help a little bit!
Kind regards
Andi