This discussion goes back forever and is useless to say which is better, akin to Mac vs Windows desktops.
This thread needed a windows advocate. There are many nice apps out there for Windows Mobile/Pocket PC devices and allow them to be on par with the Palm's. My personal preference is on the Windows side, especially since I can carry all of UpToDate on my handheld. Yes, many images are missing, but most tables are present, as is nearly all text. Besides, buying it also gives you a copy for your personal computer, so you can have UpToDate with you regardless of whether or not you have wireless access to your school's network. It's been invaluable to have UpToDate with me anywhere I go. Yes, most schools have it freely available on any terminal and I realize it. However, until you've tried the convenience of carrying the reference with you, you'll never truly understand how nice it is. Is it expensive? Sure, but it's worth it. Consider how much you spend on med school and then ask is adding another $250 ($195 cost + $50 for memory card) really a big deal. Nope, not if it helps you to be a better doc -- it's an investment.
I write software for both Palm and Pocket PC devices and have been doing so for eight years. I find the Palm can be quick and efficient, but it also lacks some capabilities the Pocket PC can handle. So, my apps on the Pocket PC tend to be more complex because I can do so much more on the Pocket PC side. Do you have to pay for some apps on the Pocket PC side that might be free on the Palm side? Sure, but the prices are often very reasonable and, again, can be viewed as an investment in your medical education. Besides, what's wrong with the developer getting a little money for their time?
Finally, any app that can run on a Palm can also be run on a Pocket PC using the Palm emulator by StyleTap ($50). So, if there's a killer app on the Palm side, but you'd really rather just get a Pocket PC, consider StyleTap. I have it so I can show folks my Palm software on my Pocket PC and find it's very convenient to use.
Hopefully this helps folks on the fence.