I have done the review of both Redmi 5A as well as the Tenor D handset. I am going to talk about specific things that are different on both these handsets. Tenor D may look good but in general Redmi 5A has better features.
Tenor D Vs Redmi 5A Comparison
Design
Both handsets look different, body made of plastic, curvy design. Redmi 5A is smaller in size when compared with the Tenor D (10.or D). 5A is no doubt lighter. Tenor D is using on screen navigation buttons and Redmi 5A comes with dedicated navigation buttons. Both handsets come with triple slots – 2 SIM + 1 micro SD card.
Screen
Redmi 5A comes with 5 inch screen with 1280 x 720 pixels resolution. Tenor D comes with 5.2 inch screen with 1280 x 720 pixels resolution. So you get a bigger screen on the D when compared with the 5A.
Now most of the non technical guys with get happy with this and prefer the Tenor D, but there are two things. I find the Redmi 5A screen quality better than the Tenor D and the 5A screen supports 10 point multi touch. Guess what tenor D supports just 2 point. All premium handsets come with 10 point multi-touch support and 5A is offering that for Rs. 4,999.
There will not be any issues using 2 point multi touch screen but with more multi touch options you get smoother touch experience and specially with apps that support more than 2 point multi touch.
Finger Print Sensor / IR Blaster
Now finger print sensor is missing on the Redmi 5A but the handset does come with IR blaster. The Tenor D does come with finger print sensor and IR blaster is missing. A personal choice here, depends on what you want.
Sensors
On Redmi 5A you get Accelerometer, proximity, light, step and magnetic sensor and on the Tenor D you get Accelerometer, proximity, step, magnetic and gyro sensors. Gyro sensor is useful when using VR application, also VR looks best with 5.5 inch screen. Light sensor is missing on Tenor D which means you will need to manually control the brightness.
Performance
Both handsets using Snapdragon 425 quad core processor that is good for normal usage not really for gaming user. Performance is the same.
OS
Redmi 5A comes with MIUI 9 that offers unique user experience whereas the Tenor D comes with stock android with limited customization. MIUI offers a lot of features that you get on premium smartphone. Again a personal choice here.
Camera
Both handsets are using 13MP rear and 5MP front camera. Camera quality on both the handsets is average, however the camera quality is slightly better on the Redmi 5A.
Battery
Redmi 5A houses a 3000 mAh non-removable battery and Tenor D comes with 3550 mAh non-removable battery. Screen is bigger on Tenor D hence it needs extra battery juice. Also battery life is slightly better on the Tenor D.
Conclusion
As you know now that there are certain things missing on the Redmi 5A and certain things on the Tenor D. Screen quality / multi touch is better on Redmi 5A, also the camera quality is better. Tenor D has finger print sensor if that is what you need, but note light sensor is missing.
My choice would be the Redmi 5A that technically offers more for the price. Though Tenor D is also a very good option and is indeed competing with 5A.