i will look for a trusted supplier. i seem them priced at 15 dollars.. it seems like ppl are suggesting that i go with the iphone 4s locked and buy a gevey ultra... is this correct?

Which iPhone 4s do i buy? I want to buy an iphone 4s. I live in Israel and I will be in USA during April and then returning back to israel I want to know if i buy 1. iphone 4s unlocked Factory - about 650 ish on ebay, 650 on amazon 2. iphone 4s unlocked via Gevey Sim - about 600 3. iphone 4s...