Comment by jbstack

There is actually scientific evidence that direct engagement with material (e.g. making notes, re-writing in your own words, completing exercises, explaining it to others, etc.) is very beneficial to memory formation.

So, although creating a card is similar to reviewing it once (in that they will both help you remember it for a while), the former is worth more than the latter as a "unit" of memorisation. This means that you'll likely have longer review intervals, and therefore spend less time on reviews, if you wrote the card yourself, because the memory starts out stronger.

That has to be balanced of course with the amount of time you spend writing the card vs the gains you make in saved review time from having done so.