2-p is correct that "pressure is pressure." Black powder does not produce the low pressure some people imagine. It is very easy to load or (now) buy loads of known low pressure - actually lower than the BP. The main issue with early nitro powders was that controlling burn rate was not well understood. It was easily possible to overload shells. Also, there was a race to make high velocity loads and some of the older guns were not up to the newly possible pressures. Nitro got an across the board bad rap.
Some peole just plain enjoy BP with all its needs. Others can benefit greatly in the shooting of older guns with appropriate nitro loads and the reduction in needs. If you can shoot a cartridge gun with BP, it is possible to shoot it safely with nitro. The key is to fully inform yourself before you pull the trigger the first time. If you don't know it is safe, don't do it. Period. If you hesitate to shoot a gun with nitro, hesitate equally to shoot BP. Fortunately, there is a world of information availabel in this time.
