Let's consider for a moment that you, personally, have two different controllers. One has sealed batteries and can be charged via any of the micoUSB cables you have available. One takes 2 AAs. You have two batteries in the controller and two in a charger.
Which controller takes more *effort* to keep charged over the course of a month?
That's really a question of preference. If you ask me, it would take considerably less effort to keep my controller that is chargable via USB cable in a usable state than it would be to find that charger with the two batteries in it. Why?
Because I don't have a single device that still relies on AAs. Ergo; no need for a charger or the batteries. Most of my electronics can be charged over a USB cable - my tablet, my smartphone, my GoPros, my headset(s).
In fact, having 3 controllers (total of 6 if I include the PS3 controllers), I would need far more batteries and chargers to keep up with keeping them up in a usable state, given I have at least 3 USB chargers lying around (and not counting the servers with a USB port that could be used as well). The good thing with charging over USB is - even if I had 4 'active' controllers, it's far more likely I'll find 4 USB cables and 4 ports to charge them than wanting to have a set of 4 pairs of batteries and potentially another 4 pairs as spare and perhaps an extra charger to keep them charged at all times - then, having to worry about if I actually charged them or forgot to - or worse, which batteries belong to the same pair (as they shouldn't really be mixxed).
For amusement sake; what if all your devices (yes, even your smartphone) had rechargable AAs - would you still find it convinient? I'm willing to bet you find it convinient now with the controllers because it's foremost one of the few devices that still requires it.
Fair play if you find batteries more convinient, but IMO, I'm glad they are more or less a thing of the past. Never looked back and never will.