These handles are just like some on other well known cars, and are really what Tesla should have done all along. They aren't as "fancy" as the Model S handles, but they are far more practical, and serve exactly the same purpose as far as drag goes.
As to why Tesla did it, I'm sure it's not because these are better (which they are) because Tesla loves flashy, it's because these are far cheaper, and they need to find ways to save some money if they're to hit the price point in the model 3. It doesn't hurt that these are also more reliable, and lighter weight, all of which are good things.
As for left vs right handed, as was pointed out elsewhere, when you approach a car, you generally want to use whichever hand is closer to the hinge to open the door, this opens the door away from you so it's easier to get in, as opposed to towards you which is always awkward. I know we wouldn't normally even think about such an automatic thing, but pay attention next time you approach a car, and even try using the other hand than the one that naturally reaches for the handle, you'll find this is the right way to do this, right handed on the right side of the vehicle, left handed on the left.
As for the different handles on the different cars at the reveal, I'm sure they needed every prototype they could get for that reveal, so used various ones from various times, I bet their first ones started with the MS shape, and later they decided to go with the L instead. I think the L is better. Keep in mind, there's still a lot of time for the design to change yet, and I suspect many things will (for instance I'll be SHOCKED if that touch screen doesn't get recessed in to the dash)