What is the fastest to load the phone?

Hello in theory this is a easy question , or not?

nokia n900 original charger ac-10e

-5v
-1200ma
-whole mains charger

nokia charger ac-50e

-5v
-1300ma
- charger with USB input (plug in the ca-101 cable for charge)

Battery n900

- 1320mah


The better option I think is the ac-50 but ,
can be harmful? , by some motive

I think that not , but I prefer to ask .

What think do you?