I am taking social science courses only, therefore typing has become essential to my studying. I would never be able to get the same amount of lecture content written down as I do with typing my notes out. I have a MBP and an iPad.
I find that some classes I prefer to sit and listen as opposed to get every single word typed out, therefore I pull out my iPad. If I need to get everything down, I pull out the laptop. I suppose I could just get a wireless keyboard for the iPad and get everything done on the iPad, but it comes down to software. If you like to take notes while using bullets and tabbed bullets, I have yet to find an iPad app that nicely tabs bullets as you write. So, if I need to get tabbed bullets into my notes quickly, I pull out the MBP. If I have time to hit the space button 10 times to nicely line up my bullets, then I use the iPad. Seems a bit obsessive, but I like organization.
Having said all of this, two other things point in the direction of the iPad. First is battery life. I have 8-10 hour school days and no laptop lasts that long while using wifi and Bluetooth. The iPad is king when it comes to battery life.
Second is the fact that the screen is always full-screen, and as mentioned earlier, eliminated many of the distractions that a laptop has.
I think a lot of this is personal preference. If anyone knows of a note-taking app that formats bullet lists properly, please let me know!