I have a co-worker selling an iPhone 5s gold 16GB for Boost Mobile (The carrier I work for) for $400. Problem is that Sprint or their subsidiaries have issues with getting phones unlocked. They also seem to lose their value the quickest in the market. So should I just stick with the 5c I've got on that carrier and spend a tad more to get an unlocked version? Is there a difference between Verizons model and the unlocked version that can be bought from Apple? Thanks.