This news could potentially disappoint a few folks who are excited about the new Samsung Galaxy S4. There has been speculation as to why several different versions of the device, including the U.S. version, were going to get the Snapdragon 600 instead of the Exynos 5 Octa-core. One of the predominant theories was the Samsung had the same problem with this Exynos chip that they had with the previous one, namely it has compatibility issues with LTE radios. Sadly, that is not the case at all. Samsung themselves confirmed on Twitter that the Exynos 5 Octa is perfectly compatible with all 20 of the primary LTE radio bands.
We've reached out to our sources and most of the intel suggests the real reason the U.S. (and several other) versions of the SGS4 will come with the Snapdragon 600 instead of the Exynos 5 Octa is due to supply issues. Apparently, the yields are low for the new super-chip from Samsung, so they had to work out a compromise that was compatible with their shipping schedules. The only bright side to this news is there is now potential for a future revised version of the SGS4 to come out in other countries that includes the Exynos 5 Octa, if they can eventually work out the supply limitation issues.
Source: Twitter - Samsung