RAW, then open in Camera Raw, convert to grayscale and adjust the luminance levels, then open in Photoshop CS6 and dodge, burn & curves the hell out of it until I love it. I prefer having 100% control on how every detail looks.
I would say shoot in color and convert in post in almost all cases as it gives you greater creative freedom. As Fallis has said, DSLRs are designed to give very low contrast images right out of the camera. This is to maximize your options in post. The one exception would be if you have a deep budget and a very strong love of b/w and so choose to invest in an expensive black and white only camera such as the Leica AG ([link]). B/W only sensors give up the ability to ever capture color in favor of a sharper and higher quality image because each pixel of the sensor is able to record true luminance values rather than having to capture an RGB color.
I don't think there is any solid rationale for shooting in B&W rather than removing color in post-processing. It's like buying a loaf of toasted bread. Toast can be quite tasty, but if you want soft bread, you can't untoast it.
And then there's the clowns who use "colorize" in Photoshop to add color to B&W. That's like microwaving a piece of toast wrapped in a wet paper towel. Now it's even WORSE.
Actually, hand coloring film photos dates back at least to the American Civil War, and coloring b&w photos can be quite effective. The thing is, they have to be shot in a certain way in order to get a good result. If you don't plan for it and set the exposure a little under, before you trip the shutter, you are not going to have a good base for coloring. Coloring a normally exposed b&w photo will usually result in something that looks like crap. The problem is that adding pigment to something that is dark already doesn't just color it, it makes it darker. You won't be able to use any subtle coloration, because the base will be too dark. You would have to slather on the color in order for it to show and it will not look natural.