Does it give you a better photo to put the camera in b&w mode vs taking the picture in colour and making it b&w on the computer?

I don't know. Why don't you try it and find out. Then you can see which one you like better.

Taking in color and making it black and white is better.The best way is the Channnel mixer in photoshop...
http://www.cambridgeincolour.com/tutorials/color-black-white.htm
..and also there are many actions and tutorials on the net
http://www.atncentral.com/download.htm

Thanks. :D