they re all good - but the battlecruiser would have to be bigger - its roughly twice the size of the destroyer.
the BC appears to have a thickened hull - maybe you can do it for the battleship, too. - and for whatever reason, i don t really like the vertical wings on the tail of the battleship. ( the ones on the sides )
splitting the mainframe of the ship on the battleship is good. ( even if its not a deep split anyway ) - ... there are windows missing in the front part of the battleship - its big enough to show more than just the bridge.