Stay with sidekick or use samsung gravity 3?

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well i had a sidekick for 3 years, i stopped using it a year ago its the sidekick LX. now my mom was just about to turn off her tmobile but tmobile sended her a phone for free so she could stay, it was the samsung gravity 3 she said i can have the phone and put a prepaid card in it or i can use my sidekick and put a prepaid card. The aim on the sidekick is better, but the camera on the gravity is better. plus the gravity is new, ughh i dont know what to choose help me