Each rifle will have its own preferance for ball and load. You will have to shoot each size and let the rifle tell you which is the better. Make sure you use enough patch, although having a super-tight fit is not as necessary as some think.
Note the last paragraph of this page regarding patch fit. Do keep in mind that he is talking informal target shooting, not hunting loads. Also keep in mind that I was taught black powder rudiments by a grandfather who grew up without a cartridge firearm until after he was married and had kids. He liked snug, not hammer-em-home fit.
I like the looser fit, and will drive a lubed wad on top of the powder to get a better gas seal, just because I'm a bit anal about such things.