I say get the RIM one because right now nobody really knows what charges and doesn't charge it. I have a 2.1 amp and it won't charge my phone so your best bet is one made by RIM.
The RIM ones are the best. Most other chargers that have a USB port are wired for Apple devices and will not charge the new BlackBerry phones without a specialized charge only cable.
Make sure it is a good one as a friend purchased one and it near caught his car on fire. The cable shorted and burnt the console and seat to the point it was smoking from the melted padding in the seat. The device need to have it's OWN breaker as the car breaker is way to high of an amperage before it will blow.
