This is just useless.
Fact of the matter is that when you buy a subsidized phone from a carrier or they give you the phone for free especially smart phones they lock you in for the contract.
That contract if completed with the requirements for the phone makes you pay the full unsubsidized price + more when the 2 years are completed. Now if you buy a CDMA phone you can only take it to another CDMA network (Sprint, Verizon, Virgin Mobile, Metro PCS, etc) and if you buy a GSM phone you can only take it to another GSM network (Att, Tmobile, etc)
So it is best to just buy your own unlocked GSM or CDMA phone and use it on the carrier you choose.