Can anyone explain the difference between using CDMA (verizon based i think) and GPRS (cingular/ATT based)? Is one better than another both in preformance and overall cost?
Actually, you probably want to look at it as CDMA vs GSM which is really a form of TDMA.
The difference has to do with how cell phone carriers multiplex multiple simultaneous calls within their allocated frequency channels. Both use digital transmission technology but the basic underlying modulation and multiplexing technologies are completely different and incompatible.
CDMA is very ingenious and uses a spread spectrum approach to allow multiple calls per channel. GSM uses TDMA which essentially multiplexes the signals in the time domain, by chopping them up into packets and then re-assembling at the other end.
It's generally agreed that CDMA ultimately allows more efficient use of the bandwidth and the GSM camp is actually moving towards a CDMA solution of their own (eventually).
From the consumer perspective, either system will work fine IF you have good coverage. It's all about coverage.
Because GSM is more common world-wide, there are more options in the phones themselves in GSM.
I wouldn't hesitate to use either depending on which carrier has the best coverage in my area and/or is offering the best deals. But if you switch, you'll need a new phone.
There IS a practical difference between CDMA and GSM; which is where the user account information is stored.
In most CDMA phones, the information is stored within the phone. If you change phones, you need to get the new phone activated by your cellular company.
GSM stores your information, as well as phone numbers on a "smart" card, which means that you can simply remove the card and put it into another compatible phone and have account and phone numbers transferred to the other phone.
Addiitionally, if you are travelling to Europe, you can bring your GSM card and put it into a European frequency GSM phone and use it there. Alternately, you can get tri-band GSM phones that work in the US and Europe.
