Smokeless powder technology may have killed off most of the old blackpowder loads. But cartridges such as the .270 and 30/06 do not kill better, or perhaps even as well, as the old blackpowder big bores. They just allow you to hit more easily at longer range while still providing respectable killing power.
I've been looking for a while for a quote from one of the gunwriters of the transition period to smokeless powder. He said the smokeless loads were easier to hit with, and killed better, than black powder loads. I think it was Whelen, but can't find it. It may have been a comparison like 32-40 to 30-40, not big bore.
