Personally, I'd go with the .50. It's more versatile.
.45 is usually the minimum legal calibure for whitetail deer.
If you hunt bigger critters or oinkers, you have to go with the .50.
Actually ... if I'm hunting boar, I prefer a .54 using the heaviest conical I can get.
For strictly target shooting, flip a coin. Both are accurate.
The difference in cost to shoot is negligable; at worst two or three cents.