What nuance does "ことなく" have?
If we compare the following two sentences:
(For example, at a footrace:)
Is ことなく stronger than simply saying ないで? Does ことなく show will and volition more than the ないで version?
I think both conveys the same meaning. ことなく is though a bit more formal. For example, you'd be a bit surprised if a 10 year old would say ことなく, whereas ないで would be very common.
However, ことなく can be used in colloquial usage, especially if you are using 敬語. Even when you are talking in non 敬語, you can still use it.
To summarize, ことなく is a tiny bit more formal than ないで.
They mean the same thing, but my book says that