MacBook. But it depends.
I swear I've never been happier with mine, especially since I've had no issues with any of the 5 I own (I've been a Mac user since 2005).
However, an iPad is a great tool. I used to take it to school everyday, whereas my Mac only came with me when I needed projects done or the like. My iPad was perfect for taking notes, while recording the class, and I would switch between the Net and my Textbook all at once. I literally used to go to school with my iPad in hand, Phone and Wallet.
And then you'd see people lugging around a Laptop bag, school bag full of books etc.
A MacBook makes sense for Projects and more in-depth work. But even with a Mac case or whatever, it still just wasn't as handy as having my iPad.
Also one thing to note, is an iPad advertises 10 hours battery life, and you pretty much always get a full day or two out of it. With a Mac, I find you get about 10 hours of typing and such, but as soon as you start watching video or browsing the web, that time is reduced by a few hours. Whereas Web Browsing seems fine on an iPad. I've watch an entire 10 Episode TV series (50 mins each) on a single iPad charge.
I also have the same issue with my Windows Laptop (
Lenovo x220T) I would get all day battery by typing up documents and light web browsing, but I'd watch a movie after charging and when it's done I'm at like 50%. Watch a second movie and I'd have to plug in.