Just my own personal experience.... I changed the oil in my 126 a little bit ago. I DRAINED it, had it up on jack stands and then I also took the pan off for a gasket (and powdercoated the pan)....and there was hardly anything left in the bottom of the pan. Not near what the picture of 7oz looked like. Of course there was a little something, but not near enough to warrant buying a $50 pump.
Also I go to college and don't exactly want to be lugging this extra piece of equipment around.
I don't doubt that the Topsider works just fine and the ones that have it love it. Nothing wrong with that. But for me at this time, draining is better