It's all about cables too. I have a 2 amp TomTom charger hooked up to a 3 metre long USB cable but it charges slower than the standard 'in the box' charger Sony supply at 1.5 amp.
More cable and wrong core rating = more energy lost or wasted. I actually had to ask a sparky about this one, but it's true. Cable length, rating and core make all the difference.
If you hooked up a 3 amp charger (I had one for an old phone) to a cable that can only handle 1 amp then you will only get 1 amp into the device, probably melt your cable too over time.
Honestly, the best bet is to use as near as dammit to the original rating on the included in the box charger. Electricity is a funny thing, it can screw your phone up in ways only time and noting the battery life will show.
Sent from my C6603 using xda app-developers app
If it's broke, use a hammer. If that fails, you're not using a big enough hammer.