Not all "smart" chargers will work with all devices. My anker one will only push 450mA to my note 2, whereas a cheap generic one with the data pins shorted will go to 1.2A on the charger doctor to the same phone with the same cable.

Do not believe what the software on the phone reports the charge current to be.

The smart ones have a chip in them that tries to identify if you have plugged in an apple device and give the voltages that apple in their infinite wisdom decided to use to signal the chargers capability, rather than just implement a current limit in the charger like every other charger since forever has done.

The only difference is with newer phones with quickcharge 2 where they negotiate with the phone to give it a higher voltage. The phone has a buck converter in it dropping the voltage, rather than the resisitive dropping that most lower power devices use. This means its cooler and more efficiant. But only phones that negotiate will get the higher voltages. If you plug a QC 2.0 phone into a dumb charger, its slightly faster than a resistive charger but maybe 15% or so?

The usual cause of slow charging is because the "smart" chip is presenting itself as an iphone charger, and the phone is going "WTF is this" and thinks its charging off a PC, where you can only pull 100mA before you negotiate with the PC for more.