I've had a number of different models by different manufactures and, to be honest, haven't been able to see any real differences between them. All have worked reliably and have been very useful.
I do, however, really love my Sony Micro Vault USB 2 model. It's noticably quicker when transfering files if it's used on a PC with USB 2 sockets and the design appeals to me!!
I know that many people knock Watford Electronics for poor aftersales support(not something I've discovered yet) but they are offering their own brand device at an excellent price.