Well, I'd put it in a different perspective.
I like to lug around a swiss army knife, because a toothpick doesn't do the job.
I drive a motorcycle because a matchbox car can't get me anywhere.
toothpick = Kindle (lightweight perfect tool for one small specific job)
Swiss Army Knife = iPad (portable multi function device - perfect for a variety of common everyday lightweight needs)
Tool Box = MacBook Pro (Portable, albeit somewhat cumbersome catch-all giving you ability to tackle almost any job)
Work Shop = Desktop (immobile but complete solution to handle any job in the most robust and fastest way)
I like the motorcycle analogy, but:
motorcycle = iPhone (small, fast, spontaneous, easy to park just about anywhere - terrific solo experience, but also limited to the solo experience and not particularly good at hauling much around for work)
Porche = iPad (a little bigger, but still pretty compact, really fast, handles well with a great user experience. A thrill to operate, FUN, pretty easy to park even in tight spaces, but also good for sharing the experience with someone else. Easy to throw a Briefcase worth of stuff in it, but not a whole lot more - note: a lot of people don't need a whole lot more)
Pick Up = MacBook Pro (a terrific well built machine with enough power to handle not only your personal needs but all your extra work baggage, as well, capable of handling just about anything you throw at it. Capable yes, but fun? Arguably, moderately fun, but also isn't as convenient to park in tight spaces. Most importantly, a lot of machine to lug around if it's not being used to capacity.)
They all can get you places. They're usefulness depends on how much you need them to haul - how much you need to ask of them. Everyone's needs are different. I may even need a pick up if I am in construction, doesn't mean I don't want a porsche when I'm off work.