I misunderstood your question when I responded with the rimfire comment. If you are looking for a durable finish, I think it's sort of a tossup between the Glock "tennifer", and stainless steel offered on other brands.
Here are the pros and cons--
Tennifer (and similar from S&W, Walther, etc.) pros: VERY rust resistant, very scratch resistant
Tennifer cons: finish is actually almost the natural color of steel (off-gray color) and requires an outer coating of oxide to be dark in appearance. This outer coating CAN be worn off through normal handling, holstering, etc.
Stainless steel pros: fairly rust resistant, but NOT as good as tennifer
SS cons: tends to show scratches easily, so duty "wear and tear" is more likey to be pronounced on any polished stainless.
In my opinion, the BEST overall durability comes from the tennifer, but even that is not perfect, and the oxide WILL wear away eventually. At least if the oxide wears off, what's underneath is pretty indestructable.