Long Term Water Heater Storage-Water In Or Water Out?

Is it better to store a water heater or indirect tank with water in or water out? I figure it has to be flushed out because of the potential Legionella, but just running it in the sink, which I did just now because there was water in my electric heater, I imagine could kick out some baddies. Then also, how do you know when it's totally flushed? Maybe put a hose on it, open the relief valve and drain it that way.

Would there be less corrosion stored with water or without water? It's non-moving potable water in a tank for months.

BoilerMan said:

If electric TAPE OFF the breaker in the panel so as to not energize the elements in an empty tank!

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Funny you should say that! When I started burning oil to lighten up the tank for moving, I valved off the electric water heater, did NOT drain the tank (thankfully), and threw the breaker.
Well, the oil tank is getting near empty and an hour ago I turned off the oil boiler, valved off the indirect, and ran a faucet to flush the tank. Guess what-HOT water! At some point over the months, maybe after a power failure, I must have thrown the breakers! All's well that end well, but tape over the breaker it will be in future!