Speed an accuracy are on different dimensions that are somewhat independent.

Another consideration is how much time we can afford for the solution to be wrong and need to be tweaked. For anything that has to work the first time, you want one (two, really) of your more sober and likely expensive engineers on the case, even if they aren't your fastest.

You may or may be able to replace your 10x engineer for this kind of work, but you're likely to be hamstrung by your interview processes.