Compared to 777, American Pioneer (AP) has some advantages and disadvantages. Based on my experience on 3 inlines- Marlin MLS-54, TC XR .45, Knight Disce Elite .50.
AP is easier to ignite than 777. In a non-209 inline, it's more reliable, especially after a couple shots. For hunting, where you only fire once from a clean gun, it might not matter.
In a gun with a tighter-fitting (harder loading) sabot, like my XR .45, AP pretty much matches 777 for accuracy. It needs a little more powder, but achieves the same velocities and extreme spreads.
In my Disc Elite, which loads easier, AP cannot match 777 for velocity or accuracy. In my MLS-54 (non-209 ignition) , 777 beats AP for velocity, but is a pain to keep it going at the range after the gun gets dirty.
So, in certain guns, AP may work better.