Petroff hausser chamber is preferred for bacterial count. The main difference between hemocytometer and petroff hausser chamber is the dimensions of the chamber. The chamber depth of petroff hausser chamber is 0.02mm while that of the hemocytometer which is the Neubauer chamber has a standard depth of 0.1mm.
You cannot use haemocytometer for bacterial count as getting them into focus and counting these cells would be difficult. It all depends on the dimensions of the counting chamber.