As someone who has cut antler for Case, Buck, Queen and a score of other production and custom makers, I'll try to lend a little knowledge about the different kinds of antler.
First, nearly all, if not all, deer species lose their antler. The best antler for knife handles is shed antler because it is completely hardened and has as much natural color to it that it's going to have. And...........shed antler is a renewable resource. They grow new antlers every year and Bambi doesn't have to die for the sake of human vanity. If an antler is taken before they shed, it is not as calcified and is not generally as strong or has very much natural color. I have seen antler taken where it is light in weight and very very white, almost porcelain color. Not really good material for handles.
Secondly, most of the "natural" color on antler really isn't natural at all. Back in the day, all antler coming into the USA as raw material had to be disinfected. The method of choice was potassium permanganate. PP actually chemically changes the exterior of the antler and makes it a different color. It is not a dye, the color is a result of the disinfection stage of import/export. Most of what people think is natural color, including amber stag, is actually the reaction of the material to the PP. Amber stag occurs when the PP chemically "burns" the stag and changes it's color. Exhibition grade stag with the dark browns and purples is a result of an extreme reaction of the stag to the PP. Each horn will take on different characteristics when exposed to Potassium Permanganate. In the days of the old sheffield makers, stag was actually stained and varnished to give it color. That is done today to some extent, but only on a small scale.
The effectiveness of stag as a handle material has to do first with the species of deer, then the deer's diet.
The best species for antler material would be sambar stag. Sambar was available from India for many years, and cannot be exported from there any more. The best sambar stag in the world came from the area around Nagpur where the deer had the best diet. Sambar stag from the south of india was generally more pithy, less dense, and less colorful. Sambar stag is available from areas of Indonesia and New Zealand today. The antler from these areas is ok, but is not as dense or as textured as the India stag was. Much of what comes from Indonesia as sambar stag is actually russa deer and other related sub-species.
The next best species of deer for good antler as handle material is chital, or spotted deer. The antler is smaller than the sambar antler, but very similar in configuration with one brow tine, one coddle tine, a main beam and its spear point. The chital has nearly zero pith but also is much less textured than sambar. Most of what makers used to call sambar stag was actually chital. Spotted deer is available from all over the world including the United States, New Zealand and parts of Europe. it is not as much in demand because of its limited texture.
Red Deer is next on the list in terms of desirability. It has good texture and is fairly dense. It has lots of pith, so scales are usually cut from red deer antler. European stag, generally, is red deer. It does have more natural color on the outside, is more "white" on the inside but has less density than sambar or chital. It can, and will, warp on a knife. If dried properly and cut properly, it is a fine material. It does not have the deep grooves (generally) that sambar has. But it is a very good material.
Then there is the elk family which includes American and Canadian Elk, maral deer or mongolian stag. This is the material of last resort. Pithy and less dense than red deer, it has problems with color, texture and longevity as a handle material. It does take color nicely with PP. If dry, and if cut correctly, it can be a very nice looking material on the right knife. It does not have deep texture (generally) and is more porous than other species requiring stabilization in many cases.
Moose, mule deer, white tail deer and other species like these produce antler that have limited use as handle material. Scales from these antlers are rare. Textured rounds, crown sticks and tapers have to be hand-selected and many times must be stabilized becuase of the pith. Staining is common and some very fine handles are made from the antlers of these species. They are in the minority. The antler from these species is better suited as a craft antler and us commonly used to make furniture and all kinds of crafts.
I hope this information is helpful.
After spending nearly a decade of my life cutting hundreds of tons of this stuff, I've seen alot and the conclusions drawn above are a result of my extensive experience. Nothing is 100% and there are variations in all things in nature. I'm just attempting to give a general overview. Hope the information is of some value. I know alot about this material. Probably more than most people. Maybe sometime we can start a stag thread to talk about cutting, preparation, handling, milling, etc. etc. Until then, feel free to email me with questions. I don't claim to know it all. I do have alot of hands on experience and that's where I draw my conclusions from.
Thanks for reading.
Keep Care,
Pappy