Not that I'm a young one by any stretch of the imagination...or have one to worry about, I have both a laptop and an iPad to choose from when I travel.
As jimtherev says, it's horses for courses. I like seacue's distinction between consumers and creators of information too - I hadn't thought about these devices in this way but I think it sums it up nicely.
There's no doubt that an iPad is a neat way of keeping up with one's social network or accessing media whilst on the go (although it can quickly become costly using other people's networks!) but I don't find it suitable for real work. That said, cloud computing and the availability online of many of the applications that I use perhaps reduces the debate to how usable the keyboard is. It might be a generational thing of course - I've grown up using a keyboard and mouse to interact with these IT things and a touchscreen seems like harder work. A young one may be equally happy with a touchscreen as the primary means of interaction.
For me though, if I could only have one device, it would be a laptop - no question. But I would be wary of assuming that the next generation see things the same way as we do - remember, that old joke about having to get the kids to program the video recorder is true!