There are 2 points that were not touched on, and the first is far more important than performance, which are data security and bundled software.
Being a member in good standing at SANS.org, we have seen a steady, and almost bi-weekly report of some CEO or lowly intern loosing some portable device that held the personal SSN, credit, bank, or medical information of countless tens of thousands of people and "we didn't have a policy to encrypt it".
This leads me to the second point, bundled software. Myself being a corporate network security admin. no thought is scarier than a private data theft or loss. And nothing puts an admin out on the street or Federal prison quicker than loosing this kind of data to evildoers. Yes, I am paranoid. But that's not to say you don't value your own private information just as highly, does it?
My recommendation to you is to find a laptop hard drive enclosure that includes encryption software and a simplified one button backup function. And, no, it does not have to cost much, you can pay as little as $10. The one I use included a very advanced backup program from backupforall. This would get installed on whatever PC(s) you intend to use the device with if you intended to read the encrypted files. And like any hard drive it can hold both encrypted and non-encrypted at the same time. So the software is not required, but I highly recommend you use it.
Link to the one I use:
http://www.mwave.com/mwave/skusearch.hmx?SCriteria=AA46030
NOTE-Don't forget to get a laptop hard drive to put inside. (40-PIN ATA-6 IDE 2.5") newegg.com/Store/SubCategory.aspx?SubCategory=380&name=Laptop-Hard-Drives