I don't think you can generalise and say that B&W is always better than colour or vice versa for reportage photography. I personally prefer B&W for it removes the reality of colour and sort of forces the photographer to use the power of seeing to tell the story. By that I mean that the photographer has to find a way to convince the viewer that the story shown is valid or worth spending time to look at it. On the other hand there are times when colour is essential, the image that springs to my mind is the one of the fireman carrying the child in the Oaklahoma bombing a few years ago. Whilst it is not the type of image that we ever want to see again it was powerful but I think that the power would have been diminished had it been B&W.
Another example of good use of B&W and colour are two bodies of reportage that Martin Parr of Magnum did a few years ago, the first, in B&W was telling the story of the demise of Wesleyan Chapels in north west England and the second in colour was of New Brighton, a run down northern England seaside holiday resort. Neither would have worked but for the choice that Parr made in when to use either B&W or colour.