At my school there are both Macs & PCs for use, and I've found that, as a PC user, Macs are amazingly inconvienient. The shortcuts that help save a lot of time are different, the way you access programs & the menus are completely different - it's such a hassle that I won't even check my email on a Mac unless the PC labs have lines out the door. Of course, that all depends on whether you use Macs already or not. Also, I find the Apples overall slower than the PCs, but that could be the network here.
Apples are generally more expensive, and they claim that this makes their laptops better, because all the components are designed together. However, PC laptops are also all designed around certain chips and configurations, so I don't think that claim makes very much sense.
I have heard that Apples are more reliable and that their tech support is better, but I've had some frusterating experiences over my iPod. Perhaps the tech support varies from department to department. PCs are more likely to break down, in my experience.
I don't know how long a use-life Apples have, but I haven't heard either way so I'd assume it's about the same as a PC.
Hope this helps!