What's the advantage of writing on a computer vs. writing by hand?
The sensory experience of writing with a pencil on paper is a huge advantage for the human mind, a thing bound into a physical form with a deep evolutionary history of interacting with physical things. We hear the scratching of graphite, feel the sliding of our hand, the smoothness of paper, sense and control the muscle grip on the pencil. This more deeply connects us to what we're writing, almost as if it's a direct conduit to the thoughts themselves.
Computer writing is much faster than writing by hand. Lost are the tactile experiences beyond the rattling on a keyboard, lost are the auditory experiences save, again, the rattling of the keyboard. (It's also curious that today, keyboards are thinner, provide less tactile feedback, and are quieter than early keyboards, though a thriving mechanical 'clacky' keyboard culture exists.) The output of computer writing involves a further disconnect from the forming of letters. One finger tap creates one of many glyphs; there is little to distinguish the physical activity of one from the other. Contrast this with the muscle coordination needed to draw individual letters.
There is certainly still a ballet of activity in writing on a keyboard. Fingers find just the right letter with barely a flicker of movement from the brain or otherwise. It's a dance at 60, 80, 120 words per minute, or two key presses every second. Few things in our practiced lives happen that quickly, so some satisfaction is surely gained from this.
Quantity is an advantage of writing via keyboard, though quantity is not better in all instances. If writing something lengthy, like a novel, a paper, or a heady story, I would rather reach for a computer than papers. What is important in those words is an amalgam of reading them, not so much the words themselves, sentences, or poring over those minutiae as kernels of their own. We are to read and reflect on the sum effect of longer works, so it's less important we're connected with small letters and words themselves, more important we stay rooted in our message, which is strengthened by reducing the sensory obligations of writing by hand (the scratching of graphite may be seen as a distraction here).
But there's also the measure of attention. Where quantity is desired, attention to smaller aspects is naturally decreased. This means that writing that needs (or deserves) less attention seems better served by writing on a computer. Any number of business communications seem to deserve less care and attention than personal communications, making them a sturdy fit for typing rather than writing.
Tidiness is king when typing is concerned, so any messages needing formality, cleanliness, and organization would do well to be typed. This is emboldened by the ease with which we can alter text on a computer compared to on the page, though this renders typing on a typewriter an awkward middle between the former two.
What we'll do with the writing also matters. I wouldn't write something by hand I knew I needed to email.
It seems, then, where our attention should be when carrying out writing affects which medium is chosen. If our message is best shared as an emergent thing, gained through reading large blocks of text assimilated less directly, we ought to create in an environment that lets us forget the method and focus on the meaning. If intent is king, and small phrases, lines, or paragraphs carry a great burden of meaning, we should take the more careful analog route to involve more of our bodies in the writing process. This has the further benefit of helping us work out what we are thinking as we write, making handwritten words more valuable during the process, pulling new and varied meanings out of our minds, especially when we pay attention to words that don't "feel" right to write.
Aside:
While it's useful to think of the reading portion of writing when considering the writing itself, reading does not necessarily follow the same rules. We almost exclusively read in three different ways: glyphs on a screen, typed words on the page, handwritten words on the page. In the latter two we gain the advantage of a physical interaction with what is printed, adding tactile and auditory information. In just the latter we have a slowing of reading as we process the person's handwriting, even our own. In the former we simply have the same information delivered in a unique format, though one that does not come with the experiential analog elements.
Outside of what the reader directly gains, any text in a digital sense is consumed in an environment built for change, opening the possibility for distraction. When we can quickly toggle to something else, even if that ability is never utilized, the mind knows it may be and must put effort into not exercising those options. It is the same as standing in a woods with varying paths before us. Choosing one means not-choosing the others. With physical mediums that is nearly entirely eliminated, such that our only choices are to flip pages forward, backward, or put the text down altogether.
Digital content is easier, faster, and generally cheaper to obtain. It is also easier to archive and preserve, though it lacks the visual impact of books on a shelf, or any other sensual impact, for that matter. The middle option--printed text on a page--carries the most benefits, with the first and last having few unique benefits of their own as far as reading and comprehension go.