All the three devices mentioned in the query have their own set of pros and cons. Here we go with the comparison based on the key features.
One Plus X
The phone comes with a Qualcomm Snapdragon 801 processor. The 3 GB RAM coupled with GB internal storage makes it a good option. One Plus X has a 5-inch screen and a full HD resolution. The AMOLED screen makes its appearance for the first time in a One Plus device. The pixel density reads 441 ppi which is quite awesome. The 13 MP rear camera has f2.2 aperture which makes it a better performer in low light conditions. The issue is with Oxygen OS which has been notorious for its heavy RAM usage. This may cause your phone to experience more stutters and lags, however, 3 GB RAM is expected to take it into consideration. The phone can handle additional expandable memory up to 128 GB. It comes with 2525 mAh battery capacity.
Mi Note 3
Mi Note 3 sports an awesome unibody metal design. It comes with a 5.5-inch screen and 165 grams of weight. The full HD display assures you a pixel density of 403 ppi. The viewing angles are quite promising. There is also a reading mode that lets you have control over bright sunlight. The phone is powered by a Snapdragon 650 processor. Mi Note 3 runs on Android Lollipop 5.1.1 customised by MiUI 7.0. The UI might be familiar for those who have already used Xiaomi devices. The device has a battery capacity of 4000 mAh. The device has a 16 MP camera on the rear and a 5 MP camera on the front. The camera works great both under bright and low light conditions.
Moto G4 Plus
The Moto G4 Plus is powered by a Snapdragon 617 Octa core processor. Coupled with a 2 GB RAM, the device comes with a 5.5 inch full HD display. The best part with the smartphone is the stock Android experience you will get with the device. The device has an inbuilt storage capacity of 16 GB that can be expandable by another 128 GB. Moto G4 Plus is powered by a battery capacity of 3000 mAh. The battery supports fast charging technology.
With those points explained, I do not think there is much of a difference between the three devices mentioned here. It all depends upon your preferences. If you want a simple stock Android experience with not much of bloatware, Moto G4 Plus would be your best bet. Price wise, all three fall under the sub 15k bracket. Go for the Xiaomi device if you want your phone to support good quality photography.
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