My understand of the difference is the way the two bullets are made. The magnum are supposed to hold together better and take a larger powder charge. The standard will get the job done though. I heard they expand better and one draw back... they may not give you a pass through.

Let me first state.. I have never killed a deer with a sabot/xtp. My friend who shoots a Bighorn started out with the 240 grain standard XTP and 85 grains of powder and dropped deer where they stood. He said the wound channel was impressive. He then started testing the 300 grain standard XTP with the same powder charge. As he explained to me... when they expand they really do damage and the deer never go far and bleed real well. So I started shooting the standard 300 grain XTP because I like bigger bullets and they are so accurate in most rifles.. I just ordered 200 more of them, so I must like them. And one of these deer seasons, I will leave my roundball rifles behind and actually use these fancy inline rifles.