I seem to recall that SD was used in the US and certain countries beacause of LTE and how Exynos was not compatible. It was also noted that Exynos was faster than SD back then but no one went bat **** crazy - I guess because it only affected the Americas, China, as somewhere else. I recall even in posts here about some folks in the US wanting to buy the Exynos version and have it shipped to the US. But it really makes me wonder - why weren't more people bothered by this performance difference when it was the SD version that lagged behind Exynos?
I don't know if those LTE limitations still exist but if they don't, I agree that Samsung needs to stop this nonsense and just make the same damned phone in all regions (sans certain things that don't affect performance - like dual SIMs, etc.) and also include the same damned accessories too (it's like all phone manufacturers think including a case is only desirable outside of the Americas).
At the end of the day, I think people won't notice the difference much between the two in real world usage, but that doesn't mean people shouldn't be getting different innards, either.