Actually Management is the subject of commerce. But it can be called art as it manage all system, between employee and employer, manufacturing or producing units at artistically.
Even it can be called science as its discussion system, procedure, function and productivity is made scientifically.
In the sense, Management is the subject of commerce - Commerce means commercial arts. commercial means scientific reason.
So in this way management is the combination of science and arts.
I think management is the both art and science, you may better called it as dual process. We can not differentiate it with only art or science. While remaining in the management field you need to apply both for the success of your projects and improvement of your employees.