My son graduated two years ago with a BSEE and now works as an engineer, and my daughter will be a junior this year majoring in biomedical engineering. She is currently doing a summer research internship at one of the top hospitals/medical schools in the nation. Both wanted a Macbook Pro, and both of them are still huge fans. My son traveled a lot while in school (student manager for a Division 1 football team), and he took his iPad along on flights , which synced up seamlessly with his Macbook but was more convenient for traveling.
My daughter also uses an iPad, and she once gave me a brief demonstration of how she has her textbooks downloaded onto the cloud and accessible on the iPad, so she doesn't need to carry heavy books or the Macbook around campus in her pack all the time. Also, the note-taking ability using a stylus (pen) on the iPad is very cool, too. Some professors use a program that she can sync to that makes accessing all of their materials very seamless, but my guess is that works with a PC, too.
The ability to move between using her iPhone, iPad and Macbook to do whatever she wants is really convenient, and she has it down to a science.
My kids took, or are taking, all the undergrad math, physics, chemistry, engineering, etc., and you couldn't get them to trade their Macbooks and iPads for PCs if you tried.
My guess is that PCs and Macs work great no matter the major. It's just personal preference.