Lumia 520 is a very fastest phone
Normlly iys big issue is not getting properapp on windows store as well as in android
But windows phone shortly opened one but they give more basic apps I think basuc app was enough
And tgey included aa regular app thats not bad actully
And the uses of windows is it was faster then androd with animation
For chating propus its a very good phone you can fastly type
And windows 8.1 can update
But dont update windows 10 it support they give a official update but it habe only 512 ram so it troble in win 10
So better to use win 8.1 gives smoot feel