Not really a "best" roundball. You can cast your own, buy cast, or buy swaged balls from Hornady and Speer. Not a nickles worth of difference between the two, but some local commercial cast balls I've seen are ww or harder, not soft lead. If you buy other than swaged balls, be sure they are soft enough, or the will be tougher to load.
Patches can make a difference. Everything else being equal, a tight patch will be more accurate, but harder to load. I don't like tight patches, as long as I can get enough accuracy for hunting.
Here is a little cull taken this year with a .45 flint southern mountain rifle. Range was 65 yards, damage was substantial. He didn't run as far as some deer I've killed with modern cartridge rifles.