I'm not really sure why this question was closed. The close reason is not constructive, but it's perfectly possible to give a constructive answer - indeed, I would consider the accepted answer constructive. It's asking what makes a subset of a class of programs more efficient than others. And the answer addresses that perfectly.
It is true that this is not quite a question based on actual problems that you face. However, there are many other similar questions, that ask about computing theory, and how program(mer)s or hardware work. A recent example: How can computers calculate exponential math without overflow errors?
I would consider these questions to be on-topic, fully answerable, and generally useful to Super User.
As I said in my comment:
To the close voters: I would argue that this question is constructive - as the answer indicates, there are techniques Vim uses that make it more efficient with larger files than some other editors. That's a concrete answer, which can be supported by facts/references. And I'm not sure why people can consider this localised; there's a clear difference in how the editors handle files that affects a lot more than a small geographic area, a specific moment in time, or an extraordinarily narrow situation.
At the time of that comment, there were two not constructive votes (okay...) and two too localised votes (wait, what?). I have tried to edit the question title to be a little clearer, though I think the underlying question was always perfectly valid.
So, could we reopen this question? And if not, why? Thoughts? Reopen votes? ;)