I think that the Ipod video (30 or 60) is a far better deal, since it's only a little more expensive and it's able to play videos. The clarity of the screen is really good, and you never know when you have to kill some time ! The resin on the nano is a little thinner, which is why a law suit was brought to Apple since it claimed that the design was faulty and meant that screens could be easily scratched to the point where the display was no longer legible.
In terms of durability, if you want something that's really able to take a beating, consider an Ipod shuffle. There's no screen to scratch up, plus it's flash based, not hard drive. Hard drives are more likely to fail, so chances of a Ipod (full sized) crashing are a little more likely than a shuffle.
Anyways, I would have to say, go Ipod video ! My brother's got one and it's great !