At the at&t store and I have 30 days to return one.
Wich one should I keep?
8310 is smaller.
8820 has a better keybord but wi-fi is not much faster than EDGE and it has the 2.5 mm headset.

Thanks.

8820 has GPS + WIFI, 8310 is just GPS but has the camera. which blackberry are you more comfortable using? That will determine which one is best for you.

i would keep the 8820 because its just over all a nicer one the keyboard is a little better and the feel in your hand i feel its better and well balanced. usally all blackberry have about the same performance. i have the 8300 has a backup phone incase anything happens to my 8800 but def go with the 8820

I always used an 8300 then upgraded to the 8310. Thought it was the best thing in the world. One day, I decided to sell my 8300 since I now had an 8310. With the money from that sale, I purchased an 8820 from at&t premier for $149...to make a long story short, that was the day I packed up my 8310 and placed it in my closet.

The 8820 is such a sleek looking phone. It is more business-centric which is something so important to me while in the office. It has a great keyboard, feels like a rock, does not squeak on the sides, has a fantastic build quality, does not suffer from this "dust under the screen" nonsense, it is just overall a fantastic device and quite frankly the best BB I've ever owned.

Coming from someone who is a huuge Curve fan, the 8820 is by far a better choice, IMO.

The one you prefer. It's a subjective decision. Neither one is universally better than the other. If you need GPS or a camera there's no point in keeping the 8820. If you need WiFi then there's no point in keeping the 8310.

I think you should have said "If you need a camera there's no point in keeping the 8820. If you need WiFi then there's no point in keeping the 8310."

The 8820 has a GPS.