I was always told that submersible sump pumps were superior to the old style kind that have a float hanging down from an exposed electric motor at the top of the sump pump. I forget the reasoning now, but I think it was that if someone unplugged the pump and the motor got flooded, then the pump's motor would be ruined, and that would be it for the pump. That's not a consideration with a submersible pump as they're intended to be submerged anyway.
However, I can't say I know why submerging an electric motor would ruin it if there was no power in the motor at the time it was submerged. I don't understand why it wouldn't still run perfectly fine after it dried out completely. If anyone could explain this, I would be eternally grateful.
I believe I've seen Little Giant submersible sump pumps for sale at my local "McDairmid's" hardware store, so I'm not sure it's fair to say that you can't get a decent sump pump from a corner hardware store. I don't expect Little Giant makes good pumps when it's shipping them to plumbing wholesalers and crap pumps when it's shipping them to small, privately owned hardware stores. I expect Little Giant makes the best pumps it can for each and every customer it has who buys Little Giant sump pumps. Or, rather, I'd be very surprised to learn different.