I had a Nokia Lumia 435. It was my first phone but now I am using Lenovo Vibe K5 note for about 6 months and here is my opinion about Windows phone.
1. Windows phones are not user friendly. Unlike Android or iOS these Windows phones are very difficult to understand.
2. In Windows phone we can share or get any song, image or any application from other devices which we can do easily on Android.
3. From last few years there are a very least amount of applications and games available for Windows platform mobiles and recent time meny developers or not releasing their application in this platform.
4. The performance of Windows phone is not good enough. Is you skip any updation on your device you will receive various lags in your phone.
5. The security system of Windows phone is very strong and reliable. This is a plus point of the phone
6. You can do any kind of work in this phone like you can do in your PC and the battery backup of this phone is very good.
7. The most valuable point of this phone is if there is a lack of internal storage in this form you can use SD card to install applications on it which you cant do in Android devices
All I can say though this phone is now outdated in these days but it still very reliable and perfect for regular use.