I have a Dell XPS M1330 (13") and I love it. I only use it when I travel or attend class though - have a desktop I built for all other uses. Why use a 13" screen when you can use two 26" screens? :-P
Anyway - I prefer PCs. I changed my major in college to avoid the use of a Mac. They are beyond confusing and I build/repair computers as a side job and know two programming languages. Plus, they cost WAY more.
Also - you only get a virus if you're an idiot. Encrypt your wireless, don't click on pop up ads, and don't open e-mail attachments from unknown sources. I've never had spyware or anti-virus software (7 years and counting) and I've always been virus and spyware free!
Although I will admit that Mac is idiot proof - you can't really screw one up even if you try. You can screw up a PC if you mess around too much without knowing what you're doing.
For nursing, I'd vote PC. It costs less, it is reliable, most have great warranties to save you if you drop coffee on it, drop it down the stairs, or it crashes, and the software is much cheaper and more readily available.