I've searched the forum looking for a clear answer to this but no too much success. I have been trying to wrap my mind around this but can't come to a clear conclusion. I am currently with AT&T and seriously considering switching to Sprint. I know that both these carriers have different spectrums. The question is this, by the time my contract is done with either carrier and unlock my iPhone, which version of the iPhone 5 (GSM/AT&T or CDMA/Sprint) will be most advantageous to me if I use it abroad? I know that the CDMA version has a SIM card slot but what does that mean if I use it abroad? Can I use it on a GSM network? I currently have an iPhone 4 which I am going to unlock and use if I travel in the meantime.