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?

It doesn't make a lot of difference, as it's the charging circuit in the phone that determines how much current is applied to charging the battery. Usually, this doesn't exceed about 1,000 mAh.

So, either of the above chargers provides enough power to enable the N900 to charge as fast as it will. You won't harm it by connecting it to a charger that can deliver 1A, 2A, or 3A; the phone will draw what it needs, but you don't stand to gain any advantage by using a 1.3A charger over a 1.2A one.