Pro Great picture quality
No matter the circumstances - very bright, low light, or shaky hands, pictures taken on the OnePlus 3 always seem to turn out alright. While the absolute quality falls short of the top-tier manufactures cameras slightly, the OnePlus 3 is more than competent enough to get the job done in virtually any scenario.
Pro Super fast app switching
With 6GB of RAM - 50% more than other industry-leading smartphone - the OnePlus 3 will be able to keep tons of apps loaded in memory. This means that apps won't have to re-load often, making the phone feel faster and also saving a bit of battery life (as the apps won't need to re-load which can tax the processor).
Pro All-day battery
With a 3000mAh battery, and efficient display as well as processor allow the OnePlus 3 to provide a good battery life. For all but the most demanding users, this phone will last a full day off the charger. Very heavy users may need to top it up for 15 minutes or so, but thanks to rapid charging this will be enough.
Running a full HD video for 90 minutes resulted in a 23% battery drop, and the battery has been tested to last up to 8 hours of web browsing or 13 hours of video playback under ideal circumstances.
Pro Easy notification handling
The OnePlus 3 has a notification slider with 3 positions that toggles between all notifications, priority notifications, and do not disturb mode. This is very handy because you won't need to pull your phone out and turn the screen on to change the alert profiles anymore - you can do it from within your pocket.
Pro Great fingerprint sensor
The OnePlus 3's fingerprint scanner is both accurate as well as quick to act. It also doesn't click down (it's capacitive), which means that you just need to lightly put your finger on it to be read. As a minor side benefit, one less moving button means less chance of it malfunctioning or wearing out down the line.
Pro Customizable software
The OnePlus 3 uses their own Oxygen OS. Oxygen OS provides many custmizable features. For example, just for button options you have the ability to switch from on-screen to off-screen buttons, add a long-touch option, and even the button placement can be configured (back button can be either on the left or right).
Options like these are available for other areas of the phone as well, like the built-in dark theme to take advantage of the Amoled display, and the ability to move the clock in the status bar to the left, center, right, or remove it entirely (useful if you wear a watch).