"better" depends totally on how and with what carrier you wish to use the phone, and whether you are willing to pay the full cost of the phone up front or want the carrier to subsidize part of the purchase price as part of your contract for cell service. Without knowing where you live or what your intentions are, there's no way anyone here can offer any informed opinions.
Just to make sure you understand the terms, "locked" means that a phone is restricted to use with a single cell service provider. This usually comes as part of a contract with the carrier where the carrier pays part of the cost of the phone at the time of purchase. "unlocked" means that the phone is not restricted to use with any specific carrier. For that capability, though, you have to pay the full cost of the phone when you purchase.