In my opinion it's Type-F

Because:
* It's bi-directional
* It's grounded and ungrounded plugs use the same socket
* It's already widespread
* Your fingers can't touch the live wire as you're plugging in a wire
* Low footprint

It’s bi-directional

That’s bad.

Why? It doesn’t make any difference with AC

Some people say it does with certain devices but I’ve never had anything I’ve run into. The American outlets have been used as bi-directional in most instances. (With 2 prong). If they had a ground then you can only go in one way. But that said… Obviously a cord without a ground can still plug into an outlet that has the ground set up. If the device wants the current to go in a certain direction they use one with a slightly larger prong on one side, but if you pick up any phone charger in America, you can plug it into any outlet any direction.