Exmor R sensors aren't that bad to be honest.

S4 i9505's IMX091PQ
iPhone 4s/5's IMX145
Nexus 5's IMX179
Mi4/Oppo Find 7/a/OPO and a long list of Huawei devices' IMX214
Note 4 is on the latest IMX240, the largest ever made Exmor R sensor by Sony at 1/2.6"

However, the S4 i9500 and the Note 3 was on a different sensor, the IMX135 from the Exmor RS line. It was proven to be better than the Exmor R counterparts back then.

What are your thoughts?

Exynos LTE (MY variant, Cat 4 LTE)
S805 LTE+ (SG variant, Cat 6 LTE)

These are the speeds that you would expect getting on Cat 6 LTE (N910S, SD805 variant)