If you're goin' pod, I'd go Nano.
I'm sure HDD players are durable enough for most people, but I just can't stand having one. Hearing the little harddrive spin up and down when I turn it on and off wracks my nerves. It's prone to die at any time! You -know- that if you drop it, you're going to feel that terrible feeling in the pit of your stomach. I ultimately feared carrying it with me, and so my X5L sat in my desk drawer, being used only tiny tiny blips of time due to my paranoia. Thankfully, I was able to trade it with a normal person who doesn't share my mostly-ridiculous fears.
If you have any doubt, go flash. It really takes a load off your shoulders. You're probably not as extreme in your fears as I am, but trust me, it feels so nice to have something that you can't have any legitimate worries about. (My DAP also needs to have a user-replaceable battery, for similar reasons. What if that internal dies?)