what is the difference between these drives?

Hi, I was wondering what the main differences between the Sony Dru-500A and the Dru-510A drives? I have a DW-U10A flashed to Dru-500A. I was planning on buying the DW-U14A for my brother for Christmas since it's supposed to be the OEM version of the Dru-510A. However, I heard that it is not the same hardware and cannot be flashed to Dru-510A firmware. If anyone can provide any information on this drive I would appreciate it. Thanks.