*sigh* That's one of the biggest myths out there. I can assure you that most people using their laptops outside of the house aren't running 10 programs at once, nor are they running heavy desktop apps. You can easily get just as much done, just as quick on an ipad. Sometimes using iOS apps are quicker to access information than using desktop apps.
This is simply not been my experience. When I am trying to move rapidly between multiple documents and spreadsheets, I find it significantly easier to use a laptop than an iPad.....even on the go. Once a month, I meet with our bookkeeper to update some spreadsheets for the family real estate business. I have tried it with an iPad, and it was just too awkward and time consuming. So, I bring the MBA, and everything is buttery smooth. I am talking about my real world experience, rather than Apple's marketing about iPad multi-tasking.....which kind of sucked-me-in the first place. So now, for me, it's MBA all of the way.
I accept that others might have a different experience, but this thread is asking about the MBA vs iPP, and all I can do is share how it has worked or hasn't worked for me. So, yes, if I had to choose and my workflow involved a fair amount of multi-tasking and productivity apps, I would get the MBA rather than the iPP.