Restricting automatic kernel-module loading

It's far easier to remember how to spell '1', yes, but its meaning is entirely implicit and context-dependent. In practice you're going to have to look it up every time you use it, since this is not a flag you're likely to flip often. Meanwhile, textual strings are self-describing.

(Imagine this with the block layer. It's easy to flip to the deadline scheduler, just echo 1 > /sys/block/$foo/queue/scheduler! The default, cfq, is 3, of course, because it happened to be the third scheduler added. The second scheduler was removed long ago, so 2 is not valid any more, until of course someone adds another scheduler, when 2 is apt to get randomly picked up by that instead...)