I have tried both and as far as accuracy goes, PRB's always perform better no matter the caliber. The depth of rifling determines how well a rifle will stabilize a lead conical, then the rate of twist. I did work up a very accurate load for a fast twist Great Plains Hunter barrel that I had fitted to a Cabelas stock. During all that I found that accuracy always improved with the addition of a lubed felt wad and 3F powder. Neither the Maxi ball nor the Great Plains bullets gave great accuracy and with the .50 fast twist barrel, shallow grooves, lighter was better. The Lee REAL bullets were best and I got one ragged hole at 75 yards using the 220 grain bullet, 95 grains of 3F Goes and a lubed "Wonder wad". Now, I am pretty sure that this load combination would go end to end on any elk inside of 80 yards but the recoil was brutal. I now only shoot PRB and am satisfied with both accuracy and performance.