I have shot deer with Powerbelts, Sabots, Round Ball (.58) and conicals...I have tried Pellets, APP, BH209, Black Powder, and Pyrodex.
My two cents...
Don't get me wrong... I am interested in the new stuff, but I have almost always been dissapointed. The only exceptions are with 777 powder and Blackwidow Bullets in .58. (with a different rifle, I might like BH209)
I still have not found a load that is really any better than a good old 320 or 370 T/C maxiball and 90 grains of ffg in .50 or 90 gr of ffg behind a .58 round ball. (although I do like the Black Widow bullet, they are hard to come by) and these will be my loads this year. But then again... if something "new" comes out... this old "can't resist" guy will have to try it out. Maybe someday I will really find somethign better.