Why would you lose it? Keep them organized in any number of velcro or belt clip pouches that are available on the market. To me, a portable hard drive is just one more potential gadget break. Not too mention that the better ones are pretty pricey. If you want to show the client what you are shooting, then that's another story.
I wait until after the job to start moving my files around. Away from the action in the quiet of my office I find it easier to handle things in a more organized fashion.
Don't get hung up on the gadgets. It's about photography and shooting opportunities. If you have spare cash, put it into another lens, a body, flash, polarizing filter, good software, etc.
BradT0517 wrote in post #2436422
......Although I like the idea of buying CF cards but it would be easier to lose a CF card than a hard drive.