For me, dropping in a stone attached to an O2 tank for a minute is way less effort than shaking, pouring back-and-forth, getting out the whisk or hooking up the drill with a whip on it. The O2 tank is a convenience thing for me.
It works especially well for me since I ferment in kegs now. I can stick the aeration wand in there, turn the gas on for a minute, then I'm good to go. With the mix-stir I had to take the liquid tube out when I wanted to aerate, so the blades didn't hit it, and put it back in. That was kind of annoying. Plus it splashed wort all over, making a mess. With a carboy it's fine, but anything with a wide opening, it gets messy.