Chess piece hierarchy design: inheritance vs type fields

Alternatively, if your set of classes is limited - i.e. you know the number, use a variant and visitors. For example, boost::variant<king, queen, bishop, knight ...> And the board is made up of a 2D array of this type. Now to interrogate, you can use visitors...

I would go with the class hierarchy.

For finding a piece you can keep a separeted list for each piece type. So you know where to look for each piece type.

For comparison you can rely on virtual methods too.

Another aproach is to use a component architecture (like described here: http://cowboyprogramming.com/2007/01/05/evolve-your-heirachy/), but I think it is too much for a chess game where you clealy know the types and know that those types will not change soon :).