Comparison Measures for alternatives that have the same intangible effects
Table for comparison of two alternatives
              Alternatives
Present value                 A                          B      
Benefits     $300,000             $420,000
Costs                       $200,000             $300,000
Net present value    $100,000             $120,000
Benefit/Cost ratio        1.5                        1.4

Net present value is indifferent between putting negative social/environmental effects on the benefit side or cost side.  This measure is not particularly appropriate when comparing undertakings of vastly different sizes, i.e., in example above B has a larger net present value simply because it is a larger project.
B/C ratio is not influenced by size of investment, so it is better compares different-sized alternatives, BUT there is a caveat!!!