I rarely use anything other the Sambar stag.
Teaching Moment:
The big difference is how solid the antler material is. All North American animals that grow antlers, do it via "velvet" and they grow from the outside inward. They also have a significant "pith" in the center/core. The larger the species, the larger the antler, and the more pith that exists in the antler. It's nature's way of swaying the size to weight ratio to the animal's behalf.... making the load easier to bear.
The one possible exception for North American antler is Caribou. Immature bulls have fair solid antler, but after reaching maturity, their antler becomes more "pithy" at the core. IMO it's this pith that make most North American antler unsatisfactory for knife handles. The more pith, the more you have to "fill" or "seal", and the more the antler will "move" with environment changes, not to mention being far less durable/stable as a knife handle.
Sambar antler still grows via "velvet", but the antlers grow from the INSIDE OUTWARD.... and are supplied via a single larger blood vessel that goes more or less up the center of the antler, and outwards into tiny capillaries that turn solid as the Sambar antler matures. The antler has little to no "pith", and a single hole running the length of the antler/piece. That's how to identify true Sambar stag.
About a decade ago, the tree hugger crowd managed to get an import ban placed on Sambar stag.... however, some who were importers, and met specific criteria were "grandfathered" in. That's when Sambar became super rare, and super expensive.
That also produced, and still does produce a lot of "knockoff" antler. Mainly European Red Deer, and Fallow deer antler, being sold as Sambar. Many don't know the difference, and to this day are being taken/sold antler stated to be Sambar, when it's not.
It's really easy to spot the rip off outfits, when you know what to look for. If you look at the cut end of any antler, and there is pith showing....it IS NOT true Sambar stag, even though it's being advertised as such. If you see only a solid end, with a single hole, more or less in the center, then you're looking a real Sambar.
Since the US ban came into effect, there are even "farms" in India and Europe now, that cross breed Sambar and Red Deer, or Fallow Deer, just to harvest antlers, and get around the US Sambar ban.
If you don't mind using imitation, MaseCraft Supply puts out an outstanding artificial stag.....and most people can't tell it from the real thing. It's called
"Stag-A-Like" that is about as inexpensive as it gets. I tested some of it for them way back when they first came up with it.... and I am almost ashamed to say how much I liked it.