So for units used in home mode, should we unplug it or just let it sleep?

Let me ask the question more precisely. What remains powered in the sleep mode? What are the time-to-failure implications of sleep mode vs unplugging?

I realize that there's a potential religious battle here: leave it on and risk power spikes and heat vs turn it off and risk thermal expansion wear due to cycling. I'm not so much interested in that debate as in understanding if the sleep/unplug empeg question _is_ that debate, or is sleep mode doing something else...