HydrogenOS 3.0 update now available for OnePlus 3 and OnePlus 3T
OxygenOS is an international build and has fewer updates and fixes than HydrogenOS. Because the latter is made for OnePlus users in China, it comes without access to Google services. And that means that it comes without the Google Play Store. The update to HydrogenOS 3.0 can be flashed on any OnePlus 3 or One Plus 3T model, and Google services can be sideloaded. If you come across any Chinese apps that you don't want, you can merely delete them.
The ROM, which weighs in at 1.2GB, can be found by clicking on either the OnePlus or XDA sourcelink below. Both include an installer to help you load the Google Play Store on your HydrogenOS 3.0 powered OnePlus 3 or OnePlus 3T. Besides the lack of Google services, there are other differences between the Hydrogen and Oxygen operating services, and not all are bad. For example, battery life is said to be better on HydrogenOS. Overall, OnePlus users are said to prefer OxygenOS with over 71% choosing it over HydrogenOS in a survey.
source: OnePlus via XDA, AndroidAuthority