Statistically, the PRB sheds energy quicker and the conical holds onto more energy at the same range, all things being even.
I think that whatever way you go, get a bunch of bullets and powder and head for the range. I'd spend enough time there to select an accurate load for elk, (remember you only need minute of elk to bring one home).
If you go with a conical then I would certainly experiment with a greased over powder wad; it seems to increase accuracy.
With the PRB there seems to be more variables; ball size, patch type, patch size on top of the variables with a conical; powder load and grain size.
Both PRB and conical have and will bring home elk, so make an informed choice and git to the range.
Good luck and make meat!
ET