Help with charger

Hello guys, i need help. My moto x is charing very very slow, i think it might be beacuse im using an old motorola charger.
I have another samsung charger, but its has more amp and out power. Is it safe if i use it?
Specifications of both chargers:
MOTOROLA CHARGER:
Model: FMP5525A
Input: 100-240v - 50/60HZ 0.2A
Output: 5.1V=850mA

SAMSUNG CHARGER:
Model: ETA0U80RBS
Input: 100-240v 50-60Hz 0,15A Automatic
Salida: 5,0V = 1,0A

what is the best charger to use?

Im sorry for my bad english, and thanks for reading this!