"Benediction" vs. "blessing"

Is there a difference in meaning between the words benediction and blessing? Why would one be used over the other?

Originally bless was derived from the Germanic word bletsian (meaning to sanctify with blood) and was used to translate the Latin benedicere (literally to speak well of).

So there was little earlier difference in meaning. But bless was far more productive and widened its meaning, while benediction became largely restricted to a short invocation in a religious service, sometimes now described as the blessing.

Benediction has a religious tone to it; at the end of a church service, there is often a benediction. Blessing is less religious:

My son told me he was leaving home, and after a few tears, I gave him my blessing, and he was off.

This doesn't sound as religious as benediction. So use benediction when speaking in religious terms, and blessing when you aren't.