Modularity. I can mix and match as needed.I respect you're preferences & embrace choices.
Just out of curiosity. And as one that owns & enjoys an iPad 4, MBA & MBP, what about assembling three components to replicate the form factor of a laptop appeals to you?
Open minded & a frequent annual upgrader to the latest Apple offerings, I always enjoy hearing others talk about what they use & why.
At home: iPad + MBA + Nexus 7 = 3 monitors.
On campus: iPad.
Trip: iPad + N7 = 2 monitors.
The MBA is nice, but the screen is small, not as nice to read as the iPad's, and if I am going to carry around the iPad anyhow (for reading), why not just leave the MBA at home?
Out of the house I get double the battery life, I can use the iPad in portrait, I can do handwriting, I can read comfortably, I can work anywhere (in bed, in line, etc.), and I can use Logmein to access any files / programs on the Mac if needed. Occasionally, I'll type on the iPhone (pair external keyboard with it), but usually just use the iPad. One combination I rarely do (but coincidentally, will tomorrow), is the N7 and iPad.
I don't miss the mouse a bit, because of the keyboard shortcuts (external keyboard). Navigation is a breeze.A short essay... sure. A thesis... sounds very tough on the iPad. It is definitely do-able but you might save some headache using your PC/Mac. Mouse support is crucial for me when doing word processing, spreadsheets, etc... that's one thing I like about Android.